Synthesis and antimicrobial activity of silver-doped hydroxyapatite nanoparticles.

PubMed

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

2013-01-01

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.

Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

PubMed Central

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

2013-01-01

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 Ca10−xAgx(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

Electrical impedance spectroscopy of neutron-irradiated nanocrystalline silicon carbide (3C-SiC)

NASA Astrophysics Data System (ADS)

Huseynov, Elchin M.

2018-01-01

It the present work, impedance spectra of nanocrystalline 3C-SiC particles have been comparatively analyzed before and after neutron irradiation. Resonance states and shifts were observed at the impedance spectra of nanocrystalline 3C-SiC particles after neutron irradiation. Relaxation time has been calculated from interdependence of real and imaginary parts of impedance of nanocrystalline 3C-SiC particles. Calculated relaxation times have been investigated as a function of neutron irradiation period. Neutron transmutation (31P isotopes production) effects on the impedance spectra and relaxation times have been studied. Moreover, influence of agglomeration and amorphous transformation to the impedance spectra and relaxation times of nanocrystalline 3C-SiC particles have been investigated.

Characterization of cap-shaped silver particles for surface-enhanced fluorescence effects.

PubMed

Yamaguchi, Tetsuji; Kaya, Takatoshi; Takei, Hiroyuki

2007-05-15

Surface-enhanced fluorescence has potentially many desirable properties as an analytical method for medical diagnostics, but the effect observed so far is rather modest and only in conjunction with fluorophores with low quantum yields. Coupled with the fact that preparation of suitable surfaces at low costs has been difficult, this has limited its utilities. Here we report a novel method for forming uniform and reproducible surfaces with respectable enhancement ratios even for high-quantum-yield fluorophores. Formation of dense surface-adsorbed latex spheres on a flat surface via partial aggregation, followed by evaporation of silver, results in a film consisting of cap-shaped silver particles at high densities. Binding of fluorescence biomolecules, either through physisorption or antigen-antibody reaction, was performed, and enhancements close to 50 have been observed with fluorophores such as R-phycoerythrin and Alexa 546-labeled, bovine serum albumin, both of which have quantum yields around 0.8. We attribute this to the unique shape of the silver particle and the presence of abundant gaps among adjacent particles at high densities. The effectiveness of the new surface is also demonstrated with IL-6 sandwich assays.

Aging of Nanocrystalline Mackinawite (FeS): Mineralogical and Physicochemical Properties

NASA Astrophysics Data System (ADS)

Jeong, H. Y.; Lee, H.

2011-12-01

Due to the extraordinary physical properties and high surface areas, nanocrystalline minerals have been widely investigated for their potential uses in treating contaminated groundwaters and surface waters. Most previous studies in this field have focused on either preparation of nanocrystalline minerals or measurement of their reactivity with environmental contaminants. Nanocrystalline minerals, due to the inherent thermodynamic instability, tend to change the physicochemical and mineralogical properties over time, usually resulting in the decreased reactivity. Thus, to better assess the long-term effectiveness of nanocrystalline minerals in field applications, such "aging" effects should be clearly delineated. In the present work, we have investigated the aging impact on nanocrystalline mackinawite (FeS), the ubiquitous Fe-bearing mineral in anoxic sulfidic sediments. Mackinawite (FeS) is known to be an effective scavenger for metal pollutants and a strong reducing reagent for chromate and chlorinated organic compounds. Our preliminary results indicate that nanocrystalline FeS ages via Ostwald ripening, particle aggregation, or mineralogical transformation. By X-ray diffraction (XRD) analysis, aging of nanocrystalline FeS via Ostwald ripening is found to be dominant at acidic pH. Cryogenic transmission electron microscopy (TEM) shows that particle aggregation is most evident at neutral pH. Transformation of nanosized FeS into a more thermodynamically stable greigite (Fe3S4) is observed in the presence of folic acid at acidic pH. The pH-dependent aging process may be linked with changes in the apparent solubility and surface charge of FeS with pH. The Ostwald ripening or particle aggregation of nanocrystalline FeS leads to the decrease surface area, thus causing the decreased reactivity. Given the less reactivity of greigite, the transformation of nanocrystalline FeS to greigite is also expected to result in the decreased reactivity.

Effects of gamma irradiation and silver nano particles on microbiological characteristics of saffron, using hurdle technology.

PubMed

Hamid Sales, E; Motamedi Sedeh, F; Rajabifar, S

2012-03-01

Saffron, a plant from the Iridaceae family, is the world's most expensive spice. Gamma irradiation and silver nano particles whose uses are gradually increasing worldwide, have positive effects on preventing decay by sterilizing the microorganisms and by improving the safety without compromising the nutritional properties and sensory quality of the foods. In the present study combination effects of gamma irradiation and silver nano particles packaging on the microbial contamination of saffron were considered during storage. A combination of hurdles can ensure stability and microbial safety of foods. For this purpose, saffron samples were packaged by Poly Ethylene films that posses up to 300 ppm nano silver particles as antimicrobial agents and then irradiated in cobalt-60 irradiator (gamma cell PX30, dose rate 0.55 Gry/Sec) to 0, 1, 2,3 and 4 kGy at room temperature. The antimicrobial activities against Total Aerobic Mesophilic Bacteria, Entrobacteriace, Escherichia Coli and Clostridium Perfringines were higher in the irradiated samples, demonstrating the inhibition zone for their growth. Irradiation of the saffron samples packaged by Poly Ethylene films with nano silver particles showed the best results for decreasing microbial contamination at 2 kGy and for Poly Ethylene films without silver nano particles; it was 4 kGy.

Structural characterization of nanocrystalline cadmium sulphide powder prepared by solvent evaporation technique

NASA Astrophysics Data System (ADS)

Pandya, Samir; Tandel, Digisha; Chodavadiya, Nisarg

2018-05-01

CdS is one of the most important compounds in the II-VI group of semiconductor. There are numerous applications of CdS in the form of nanoparticles and nanocrystalline. Semiconductors nanoparticles (also known as quantum dots), belong to state of matter in the transition region between molecules and solids, have attracted a great deal of attention because of their unique electrical and optical properties, compared to bulk materials. In the field of optoelectronic, nanocrystalline form utilizes mostly in the field of catalysis and fluid technology. Considering these observations, presented work had been carried out, i.e. based on the nanocrystalline material preparation. In the present work CdS nano-crystalline powder was synthesized by a simple and cost effective chemical technique to grow cadmium sulphide (CdS) nanoparticles at 200 °C with different concentrations of cadmium. The synthesis parameters were optimized. The synthesized powder was structurally characterized by X-ray diffraction and particle size analyzer. In the XRD analysis, Micro-structural parameters such as lattice strain, dislocation density and crystallite size were analysed. The broadened diffraction peaks indicated nanocrystalline particles of the film material. In addition to that the size of the prepared particles was analyzed by particle size analyzer. The results show the average size of CdS particles ranging from 80 to 100 nm. The overall conclusion of the work can be very useful in the synthesis of nanocrystalline CdS powder.

[ALEA study. Treatment of chronic wounds infected by the application of silver dressings nanocrystalline combined with dressings hydrocellular].

PubMed

Verdú Soriano, José; Nolasco Bonmati, Andreu

2010-10-01

This study was conducted with the objective to assess, in real clinical conditions in primary care and geriatric centers, application and utility of nanocrystalline silver dressings dressings combined with hydrocellular in relation to the development during 20 shifts dressing or complete healing of the characteristics of the lesions included in the study Prospective observational multicenter open, repeated measures. It could include injuries of different etiologies (pressure ulcers stage 11-111, lower limb and traumatic wounds or surgical origin), with clinical signs of local infection (at least three of the following: redness, purulent discharge, heat, edema and pain). Only one wound was included per patient. An analysis of effectiveness by intention to treat all lesions included. We recruited 103 patients who met the inclusion criteria but were collected in which 77 patients were used for nanocrystalline silver dressings in some phase of the study, They had a median of 80 years of age and 58.4% were women. By type of injury: 53.2% pressure ulcers, 31.2% lower extremity ulcers and 14.3% traumatic or surgical wounds. Over 50% of the lesions was older than eight months and a larger area of 22.75 cm2. At first, 70.1% had redness, purulent discharge 64.9%, 37.7% heat edema 42.9% and 65.8% pain. Remained in the study a median of 42.5 days at a rate of change of dressing every 2.5. During this time in 96.1% of the lesions were removed for clinical signs of local infection in a statistically significant (p < or = 0.001). 27.3% healed from injuries and those not healed, 92.9% experienced improvement, and its healing curves were statistically significant (p < 0.05). 92.2% of clinicians assessed treatment with these products as good or excellent. The use of the products used in this study consistent with the concept and PLH TIME, has proved useful in this type of injury reducing the clinical signs of infection, promoting granulation tissue and necrotic removing the burden

Process for making silver metal filaments

DOEpatents

Bamberger, Carlos E.

1997-01-01

A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

Biosynthesis of silver fine particles and particles decorated with nanoparticles using the extract of Illicium verum (star anise) seeds

NASA Astrophysics Data System (ADS)

Luna, Carlos; Chávez, V. H. G.; Barriga-Castro, Enrique Díaz; Núñez, Nuria O.; Mendoza-Reséndez, Raquel

2015-04-01

Given the upsurge of new technologies based on nanomaterials, the development of sustainable methods to obtain functional nanostructures has become an imperative task. In this matter, several recent researches have shown that the biodegradable natural antioxidants of several plant extracts can be used simultaneously as reducing and stabilizing agents in the wet chemical synthesis of metallic nanoparticles, opening new opportunities to design greener synthesis. However, the challenge of these new techniques is to produce stable colloidal nanoparticles with controlled particle uniformity, size, shape and aggregation state, in similar manner than the well-established synthetic methods. In the present work, colloidal metallic silver nanoparticles have been synthesized using silver nitrate and extracts of Illicium verum (star anise) seeds at room temperature in a facile one-step procedure. The resulting products were colloidal suspensions of two populations of silver nanoparticles, one of them with particle sizes of few nanometers and the other with particles of tens of nm. Strikingly, the variation of the AgNO3/extract weight ratio in the reaction medium yielded to the variation of the spatial distribution of the nanoparticles: high AgNO3/extract concentration ratios yielded to randomly dispersed particles, whereas for lower AgNO3/extract ratios, the biggest particles appeared coated with the finest nanoparticles. This biosynthesized colloidal system, with controlled particle aggregation states, presents plasmonic and SERS properties with potential applications in molecular sensors and nanophotonic devices.

Biosynthesis of silver fine particles and particles decorated with nanoparticles using the extract of Illicium verum (star anise) seeds.

PubMed

Luna, Carlos; Chávez, V H G; Barriga-Castro, Enrique Díaz; Núñez, Nuria O; Mendoza-Reséndez, Raquel

2015-04-15

Given the upsurge of new technologies based on nanomaterials, the development of sustainable methods to obtain functional nanostructures has become an imperative task. In this matter, several recent researches have shown that the biodegradable natural antioxidants of several plant extracts can be used simultaneously as reducing and stabilizing agents in the wet chemical synthesis of metallic nanoparticles, opening new opportunities to design greener synthesis. However, the challenge of these new techniques is to produce stable colloidal nanoparticles with controlled particle uniformity, size, shape and aggregation state, in similar manner than the well-established synthetic methods. In the present work, colloidal metallic silver nanoparticles have been synthesized using silver nitrate and extracts of Illicium verum (star anise) seeds at room temperature in a facile one-step procedure. The resulting products were colloidal suspensions of two populations of silver nanoparticles, one of them with particle sizes of few nanometers and the other with particles of tens of nm. Strikingly, the variation of the AgNO3/extract weight ratio in the reaction medium yielded to the variation of the spatial distribution of the nanoparticles: high AgNO3/extract concentration ratios yielded to randomly dispersed particles, whereas for lower AgNO3/extract ratios, the biggest particles appeared coated with the finest nanoparticles. This biosynthesized colloidal system, with controlled particle aggregation states, presents plasmonic and SERS properties with potential applications in molecular sensors and nanophotonic devices. Copyright © 2014 Elsevier B.V. All rights reserved.

Metallogel templated synthesis and stabilization of silver-particles and its application in catalytic reduction of nitro-arene.

PubMed

Sharma, Mukesh; Sarma, Plaban Jyoti; Goswami, Manash Jyoti; Bania, Kusum K

2017-03-15

Metallogel of iron-carboxylates was obtained from trans-1,2-cyclohexanedicarboxylic acid in dimethylformamide (DMF) at basic condition. Spectroscopic and SEM morphology study of the iron-metallogel revealed that the iron complex with dicarboxylic acid was linked together via carboxylates and led to a supramolecular helical like architecture. The synthesized metallogel served as an excellent template for in-situ reduction of silver ion to silver particles micro to nano scale range. Variation of AgNO 3 concentration shepherd to change the morphology of the Ag-particles. AgNO 3 concentration was found to affect the shape and size of silver particles. On going from lower to higher concentration shape of silver particles changed from spherical to large agglomerated particles. Cubic shape Ag-particles were found on treatment of 0.05M AgNO 3 solution with metallogel. Cubical shape silver particles were found to be effective catalyst for nitro-arene reduction in presence of NaBH 4 . Density functional theory (DFT) calculations were performed to rationalize the role of Ag-particles in catalytic reduction of 4-nitrophenol to 4-aminophenol. Based on DFT study, we proposed that catalytic reduction occurred via Ag-hydride complex formation. Since metallogels as well as the 4-aminophenol are finding large application in pharmaceuticals industries therefore the current work can provide an alternatives path in production of 4-aminophenols. In addition to this, the synthesis of Ag-nanomaterials using metallogel as template can pave a new direction in the development of nanotechnology and might find wide applications in catalytic industrial processes. Copyright © 2016 Elsevier Inc. All rights reserved.

Nanocrystalline Iron-Ore-Based Catalysts for Fischer-Tropsch Synthesis.

PubMed

Yong, Seok; Park, Ji Chan; Lee, Ho-Tae; Yang, Jung-Il; Hong, SungJun; Jung, Heon; Chun, Dong Hyun

2016-02-01

Nanocrystalline iron ore particles were fabricated by a wet-milling process using an Ultra Apex Mill, after which they were used as raw materials of iron-based catalysts for low-temperature Fischer-Tropsch synthesis (FTS) below 280 degrees C, which usually requires catalysts with a high surface area, a large pore volume, and a small crystallite size. The wet-milling process using the Ultra Apex Mill effectively destroyed the initial crystallite structure of the natural iron ores of several tens to hundreds of nanometers in size, resulting in the generation of nanocrystalline iron ore particles with a high surface area and a large pore volume. The iron-ore-based catalysts prepared from the nanocrystalline iron ore particles effectively catalyzed the low-temperature FTS, displaying a high CO conversion (about 90%) and good C5+ hydrocarbon productivity (about 0.22 g/g(cat)(-h)). This demonstrates the feasibility of using the iron-ore-based catalysts as inexpensive and disposable catalysts for the low-temperature FTS.

Characterization of silver particles in the stratum corneum of healthy subjects and atopic dermatitis patients dermally exposed to a silver-containing garment

PubMed Central

Bianco, Carlotta; Visser, Maaike J.; Pluut, Olivier A.; Svetličić, Vesna; Pletikapić, Galja; Jakasa, Ivone; Riethmuller, Christoph; Adami, Gianpiero; Filon, Francesca Larese; Schwegler-Berry, Diane; Stefaniak, Aleksandr B.; Kezic, Sanja

2018-01-01

Silver is increasingly being used in garments to exploit its antibacterial properties. Information on the presence of silver nanoparticles (AgNPs) in garments and their in vivo penetration across healthy and impaired skin from use is limited. We investigated the presence of AgNPs in a silver containing garment and in the stratum corneum (SC) of healthy subjects (CTRLs) and individuals with atopic dermatitis (AD). Seven CTRLs and seven AD patients wore a silver sleeve (13% Ag w/w) 8 h/day for five days on a forearm and a placebo sleeve on the other forearm. After five days, the layers of the SC were collected by adhesive tapes. The silver particles in the garment and SC were characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and atomic force microscopy (AFM). AFM and SEM revealed the presence of sub-micrometre particles having a broad range of sizes (30–500 nm) on the surface of the garment that were identified as silver. On the SC tapes collected from different depths, aggregates with a wide range of sizes (150 nm−2 μm) and morphologies were found. Most aggregates contained primarily silver, although some also contained chlorine and sulfur. There was no clear difference in the number or size of the aggregates observed in SC between healthy and AD subjects. After use, AgNPs and their aggregates were present in the SC at different depths of both healthy subjects and AD patients. Their micrometre size suggests that aggregation likely occurred in the SC. PMID:27647219

Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

PubMed

Yin, H; Casey, P S; Chow, G M

2012-11-01

Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

Prospective randomised controlled trial of nanocrystalline silver dressing versus plain gauze as the initial post-debridement management of military wounds on wound microbiology and healing.

PubMed

Fries, C A; Ayalew, Y; Penn-Barwell, J G; Porter, K; Jeffery, S L A; Midwinter, M J

2014-07-01

Recent conflicts have been characterised by the use of improvised explosive devices causing devastating injuries, including heavily contaminated wounds requiring meticulous surgical debridement. After being rendered surgical clean, these wounds are dressed and the patient transferred back to the UK for on-going treatment. A dressing that would prevent wounds from becoming colonised during transit would be desirable. The aim of this study was to establish whether using nanocrystalline silver dressings, as an adjunct to the initial debridement, would positively affect wound microbiology and wound healing compared to standard plain gauze dressings. Patients were prospectively randomised to receive either silver dressings, in a nanocrystalline preparation (Acticoat™), or standard of care dressings (plain gauze) following their initial debridement in the field hospital. On repatriation to the UK microbiological swabs were taken from the dressing and the wound, and an odour score recorded. Wounds were followed prospectively and time to wound healing was recorded. Additionally, patient demographic data were recorded, as well as the mechanism of injury and Injury Severity Score. 76 patients were recruited to the trial between February 2010 and February 2012. 39 received current dressings and 37 received the trial dressings. Eleven patients were not swabbed. There was no difference (p=0.1384, Fishers) in the primary outcome measure of wound colonisation between the treatment arm (14/33) and the control arm (20/32). Similarly time to wound healing was not statistically different (p=0.5009, Mann-Whitney). Wounds in the control group were scored as being significantly more malodorous (p=0.002, Mann-Whitney) than those in the treatment arm. This is the first randomised controlled trial to report results from an active theatre of war. Performing research under these conditions poses additional challenges to military clinicians. Meticulous debridement of wounds remains the

Influence of Particle Size on Persistence and Clearance of Aerosolized Silver Nanoparticles in the Rat Lung

PubMed Central

Anderson, Donald S.; Patchin, Esther S.; Silva, Rona M.; Uyeminami, Dale L.; Sharmah, Arjun; Guo, Ting; Das, Gautom K.; Brown, Jared M.; Shannahan, Jonathan; Gordon, Terry; Chen, Lung Chi; Pinkerton, Kent E.; Van Winkle, Laura S.

2015-01-01

The growing use of silver nanoparticles (AgNPs) in consumer products raises concerns about potential health effects. This study investigated the persistence and clearance of 2 different size AgNPs (20 and 110 nm) delivered to rats by single nose-only aerosol exposures (6 h) of 7.2 and 5.4 mg/m3, respectively. Rat lung tissue was assessed for silver accumulations using inductively-coupled plasma mass spectrometry (ICP-MS), autometallography, and enhanced dark field microscopy. Involvement of tissue macrophages was assessed by scoring of silver staining in bronchoalveolar lavage fluid (BALF). Silver was abundant in most macrophages at 1 day post-exposure. The group exposed to 20 nm AgNP had the greatest number of silver positive BALF macrophages at 56 days post-exposure. While there was a significant decrease in the amount of silver in lung tissue at 56 days post-exposure compared with 1 day following exposure, at least 33% of the initial delivered dose was still present for both AgNPs. Regardless of particle size, silver was predominantly localized within the terminal bronchial/alveolar duct junction region of the lung associated with extracellular matrix and within epithelial cells. Inhalation of both 20 and 110 nm AgNPs resulted in a persistence of silver in the lung at 56 days post-exposure and local deposition as well as accumulation of silver at the terminal bronchiole alveolar duct junction. Further the smaller particles, 20 nm AgNP, produced a greater silver burden in BALF macrophages as well as greater persistence of silver positive macrophages at later timepoints (21 and 56 days). PMID:25577195

Silver speciation and characterization of nanoparticles released from plastic food containers by single particle ICPMS.

PubMed

Ramos, K; Gómez-Gómez, M M; Cámara, C; Ramos, L

2016-05-01

Silver migration from a commercial baby feeding bottle and a food box containing AgNPs, as confirmed by SEM-EDX analysis, was evaluated using food simulant solutions [i.e., water, 3% (v/v) acetic acid, and 10% and 90% (v/v) ethanol]. Silver release was investigated at temperatures in the 20-70°C range using contact times of up to 10 days. Migration of silver from the food box was in all cases 2 to 3 orders of magnitude higher than that observed for the baby bottle, although the total silver content in the original box material was half of that found in the baby bottle. As expected, for both food containers, silver migration depended on both the nature of the tested solution and the applied conditions. The highest release was observed for 3% acetic acid at 70°C for 2h, corresponding to 62ngdm(2) and 1887ngdm(-2) of silver for the baby bottle and the food box, respectively. Single particle-inductively coupled plasma mass spectrometry (SP-ICPMS) was used to characterise and quantify AgNPs in the food simulants extracts. Sample preparation was optimized to preserve AgNPs integrity. The experimental parameters affecting AgNPs detection, sizing and quantification by SP-ICPMS were also optimised. Analyses of water and acidic extracts revealed the presence of both dissolved silver and AgNPs. Small AgNPs (in the 18-30nm range) and particle number concentrations within the 4-1510 10(6)L(-1) range were detected, corresponding to only 0.1-8.6% of the total silver released from these materials. The only exception was AgNPs migrated into water at 40°C and 70°C from the food box, which accounted for as much as 34% and 69% of the total silver content, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Using nano- and micro-particles of silver in lignin analysis

Treesearch

Umesh P. Agarwal; Richard S. Reiner; Sally A. Ralph

2006-01-01

Although there are numerous techniques available to study lignin in its various states, they all have limitations and to extract most amount of information, a number of analytical techniques have to be jointly used. We have recently started applying a new approach to lignin analysis - namely using nano- and micro-particles of silver for study of native and residual...

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

NASA Astrophysics Data System (ADS)

Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

2018-01-01

The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

Beneficial effects of polyethylene packages containing micrometer-sized silver particles on the quality and shelf life of dried barberry (Berberis vulgaris).

PubMed

Motlagh, N Valipoor; Mosavian, M T Hamed; Mortazavi, S A; Tamizi, A

2012-01-01

In this research, the effects of low-density polyethylene (LDPE) packages containing micrometer-sized silver particles (LDPE-Ag) on microbial and sensory factors of dried barberry were investigated in comparison with the pure LDPE packages. LDPE-Ag packages with 1% and 2% concentrations of silver particles statistically caused a decrease in the microbial growth of barberry, especially in the case of mold and total bacteria count, compared with the pure LDPE packages. The taste, aroma, appearance, and total acceptance were evaluated by trained panelists using the 9-point hedonic scale. This test showed improvement of all these factors in the samples related to packages containing 1% and 2% concentrations of silver particles in comparison with other samples. Low-density polyethylene package containing micrometer-sized silver particles had beneficial effects on the sensory and microbial quality of barberry when compared with normal packing material. © 2011 Institute of Food Technologists®

Fabrication and characterization of flaky core-shell particles by magnetron sputtering silver onto diatomite

NASA Astrophysics Data System (ADS)

Wang, Yuanyuan; Zhang, Deyuan; Cai, Jun

2016-02-01

Diatomite has delicate porous structures and various shapes, making them ideal templates for microscopic core-shell particles fabrication. In this study, a new process of magnetron sputtering assisted with photoresist positioning was proposed to fabricate lightweight silver coated porous diatomite with superior coating quality and performance. The diatomite has been treated with different sputtering time to investigate the silver film growing process on the surface. The morphologies, constituents, phase structures and surface roughness of the silver coated diatomite were analyzed with SEM, EDS, XRD and AFM respectively. The results showed that the optimized magnetron sputtering time was 8-16 min, under which the diatomite templates were successfully coated with uniform silver film, which exhibits face centered cubic (fcc) structure, and the initial porous structures were kept. Moreover, this silver coating has lower surface roughness (RMS 4.513 ± 0.2 nm) than that obtained by electroless plating (RMS 15.692 ± 0.5 nm). And the infrared emissivity of coatings made with magnetron sputtering and electroless plating silver coated diatomite can reach to the lowest value of 0.528 and 0.716 respectively.

Identification of Silver and Palladium in Irradiated TRISO Coated Particles of the AGR-1 Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Rooyen, Y. J.; Lillo, T. M.; Wu, Y. Q.

2014-03-01

Evidence of the release of certain metallic fission product through intact tristructural isotropic (TRISO) particles has been seen for decades around the world, as well as in the recent AGR-1 experiment at Idaho National Laboratory (INL). However, understanding the basic mechanism of transport is still lacking. This understanding is important because the TRISO coating is part of the high temperature gas reactor functional containment and critical for the safety strategy for licensing purposes. Our approach to identify fission products in irradiated AGR-1 TRISO fuel using scanning transmission electron microscopy (STEM), Electron Energy Loss Spectroscopy (EELS) and Energy Filtered TEM (EFTEM),more » has led to first-of-a-kind data at the nano-scale indicating the presence of silver at triple points and grain boundaries of the SiC layer in the TRISO particle. Cadmium was also found in the triple junctions. In this initial study, the silver was only identified in SiC grain boundaries and triple points on the edge of the SiC-IPyC interface up to a depth of approximately 0.5 um. Palladium was identified as the main constituent of micron-sized precipitates present at the SiC grain boundaries. Additionally spherical nano-sized palladium rich precipitates were found inside the SiC grains. These nano-sized Pd precipitates were distributed up to a depth of 5 um away from the SiC-IPyC interlayer. No silver was found in the center of the micron-sized fission product precipitates using these techniques, although silver was found on the outer edge of one of the Pd-U-Si containing precipitates which was facing the IPyC layer. Only Pd-U containing precipitates were identified in the IPyC layer and no silver was identified in the IPyC layer. The identification of silver alongside the grain boundaries and the findings of Pd alongside grain boundaries as well as inside the grains, provide significant knowledge for understanding silver and palladium transport in TIRSO fuel, which

In Vitro Assessment of the Antibacterial Potential of Silver Nano-Coatings on Cotton Gauzes for Prevention of Wound Infections

PubMed Central

Paladini, Federica; Di Franco, Cinzia; Panico, Angelica; Scamarcio, Gaetano; Sannino, Alessandro; Pollini, Mauro

2016-01-01

Multidrug-resistant organisms are increasingly implicated in acute and chronic wound infections, thus compromising the chance of therapeutic options. The resistance to conventional antibiotics demonstrated by some bacterial strains has encouraged new approaches for the prevention of infections in wounds and burns, among them the use of silver compounds and nanocrystalline silver. Recently, silver wound dressings have become widely accepted in wound healing centers and are commercially available. In this work, novel antibacterial wound dressings have been developed through a silver deposition technology based on the photochemical synthesis of silver nanoparticles. The devices obtained are completely natural and the silver coatings are characterized by an excellent adhesion without the use of any binder. The silver-treated cotton gauzes were characterized through scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA) in order to verify the distribution and the dimension of the silver particles on the cotton fibers. The effectiveness of the silver-treated gauzes in reducing the bacterial growth and biofilm proliferation has been demonstrated through agar diffusion tests, bacterial enumeration test, biofilm quantification tests, fluorescence and SEM microscopy. Moreover, potential cytotoxicity of the silver coating was evaluated through 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide colorimetric assay (MTT) and the extract method on fibroblasts and keratinocytes. Inductively coupled plasma mass spectrometry (ICP-MS) was performed in order to determine the silver release in different media and to relate the results to the biological characterization. All the results obtained were compared with plain gauzes as a negative control, as well as gauzes treated with a higher silver percentage as a positive control. PMID:28773531

Biomimetic synthesis of silver nanoparticles by Citrus limon (lemon) aqueous extract and theoretical prediction of particle size.

PubMed

Prathna, T C; Chandrasekaran, N; Raichur, Ashok M; Mukherjee, Amitava

2011-01-01

In the present study, silver nanoparticles were rapidly synthesized at room temperature by treating silver ions with the Citrus limon (lemon) extract. The effect of various process parameters like the reductant concentration, mixing ratio of the reactants and the concentration of silver nitrate were studied in detail. In the standardized process, 10(-2)M silver nitrate solution was interacted for 4h with lemon juice (2% citric acid concentration and 0.5% ascorbic acid concentration) in the ratio of 1:4 (vol:vol). The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance as determined by UV-Visible spectra in the range of 400-500 nm. X-ray diffraction analysis revealed the distinctive facets (111, 200, 220, 222 and 311 planes) of silver nanoparticles. We found that citric acid was the principal reducing agent for the nanosynthesis process. FT-IR spectral studies demonstrated citric acid as the probable stabilizing agent. Silver nanoparticles below 50 nm with spherical and spheroidal shape were observed from transmission electron microscopy. The correlation between absorption maxima and particle sizes were derived for different UV-Visible absorption maxima (corresponding to different citric acid concentrations) employing "MiePlot v. 3.4". The theoretical particle size corresponding to 2% citric acid concentration was compared to those obtained by various experimental techniques like X-ray diffraction analysis, atomic force microscopy, and transmission electron microscopy. Copyright © 2010 Elsevier B.V. All rights reserved.

Synthesis of silver nanoparticles by silver salt reduction and its characterization

NASA Astrophysics Data System (ADS)

Muzamil, Muhammad; Khalid, Naveed; Danish Aziz, M.; Aun Abbas, S.

2014-06-01

The wet chemical method route by metal salt reduction has been used to synthesize nanoparticles, using silver nitrate as an inorganic salt, aldehyde as a reducing agent and amino acid as a catalyst. During the reaction aldehyde oxidizes to carboxylic acid and encapsulates the silver nanoparticles to prevent agglomeration and provide barrier in the growth of particle. The existing work produces particles using lab grade chemical, here the presented work is by using industrial grade chemicals to make the process more cost & time effective. The nano silver powder has been studied for their formation, particle size, shape & compositional analysis using Scanning Electron Microscope (SEM) equipped with EDS. The particles size distributions were analyzed by Laser Particle Analyzer (LPA), structure & morphological analysis using x-ray diffraction (XRD) and Fourier-transform-infrared Spectroscopy (FTIR) confirmed the stabilization of particles by coating of carboxylic group. These studies infer that the particles are mostly spherical in shape and have an average size between 70 to 350 nm.

Suitability of different silver enhancement methods applied to 1 nm colloidal gold particles: an immunoelectron microscopic study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stierhof, Y.D.; Humbel, B.M.; Schwarz, H.

1991-03-01

In order to exploit the recently introduced 1 nm gold colloids in routine electron microscopic labeling experiments, an efficient enhancement step for a better visualization of this small marker is a prerequisite. Efficiency and reproducibility of enhancement as well as growth homogeneity of gold particles were evaluated for three different silver intensifying solutions: silver lactate/hydroquinone/gum arabic, and the commercially available IntenSE M silver enhancement kit. The best results were obtained by using the silver lactate/hydroquinone/gum arabic mixture. The quality of enhancement of the IntenSE M kit was considerably increased by the addition of the protective colloid gum arabic.

Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach.

PubMed

Nath, Soumav; Biswas, Ashik; Kour, Prachi P; Sarma, Loka S; Sur, Ujjal Kumar; Ankamwar, Balaprasad G

2018-08-01

In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 °C temperature.

Solvothermal synthesis of nanocrystalline TiO 2 in toluene with surfactant

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Choi, Byung-Chun; Seo, Hyo-Jin

2003-10-01

Synthesis of narrow-dispersed nanocrystalline TiO 2 was investigated by surfactant-aided solvothermal synthetic method in toluene solutions. Titanium isopropoxide (TIP) was used as precursor, which was decomposed at high temperature in the surfactant-dissolved solution. After the solution was thermally treated at 250°C for 20 h in an autoclave, low-dispersed TiO 2 nanocrystalline particles with average size of <6 nm were synthesized. When sufficient amount of TIP or surfactant was added in the solution, long dumbbell-shaped nanorods were formed, which may be due to the oriented growth of particles along [0 0 1] axis. Characterization of products was investigated by X-ray diffraction and transmission electron microscopy.

Contribution of the hydrostatic pressure to the shape of silver island particles

NASA Astrophysics Data System (ADS)

Anno, E.; Hoshino, R.

1984-09-01

We have investigated the shape change of silver island particles caused by the surface energy reduction. When the surface energy was reduced by the reaction with hydrogen sulfide, the flattening of the particles was observed. As is well known, the similar shape change takes place when the particle size increases. Therefore, the particle shape is considered to depend both on the surface energy and the particle size. From this consideration, we predict the contribution of the hydrostatic pressure P to the particle shape. As evidence of this contribution, we consider the existence of the critical size below which P is larger than the adhesive force FA between deposit and substrate surface. Investigating the influence of the flattening due to the surface energy reduction on the size distribution, the critical size is found and estimated to be about 80 Å in diameter. This value is comparable with that estimated from the condition P = FA.

Deposition and characterization of ZnSe nanocrystalline thin films

NASA Astrophysics Data System (ADS)

Temel, Sinan; Gökmen, F. Özge; Yaman, Elif; Nebi, Murat

2018-02-01

ZnSe nanocrystalline thin films were deposited at different deposition times by using the Chemical Bath Deposition (CBD) technique. Effects of deposition time on structural, morphological and optical properties of the obtained thin films were characterized. X-ray diffraction (XRD) analysis was used to study the structural properties of ZnSe nanocrystalline thin films. It was found that ZnSe thin films have a cubic structure with a preferentially orientation of (111). The calculated average grain size value was about 28-30 nm. The surface morphology of these films was studied by the Field Emission Scanning Electron Microscope (FESEM). The surfaces of the thin films were occurred from small stacks and nano-sized particles. The band gap values of the ZnSe nanocrystalline thin films were determined by UV-Visible absorption spectrum and the band gap values were found to be between 2.65-2.86 eV.

Low-Temperature Sintering Behavior (≤ 400°C) of Micro-sized Silver Particles Decorated by Silver Nanoparticles Through Surface Iodination

NASA Astrophysics Data System (ADS)

Zhou, Jian; Tang, Hongbo

2018-05-01

This paper introduces a facile and effective route to decorate micro-sized silver particle surfaces with Ag/AgI nanoclusters through a wet chemical reaction at room temperature using iodine and ethanol as reactant and solvent, respectively. Photosensitivity of AgI is utilized in the route, and AgI decomposes into Ag upon contact with sunshine, forming Ag/AgI nanoclusters. The modified micro-sized Ag particles showed sinterability even at 200°C and formed rigid electrical conductive networks at 350°C. Moreover, sintered film containing the modified Ag particles reached the best conductivity, 9.35 mΩ/sq, after sintering at 350°C for 20 min, while the film with untreated control Ag particles obtained its best conductivity at 400°C. The excellent sinterability should be attributed to the nanoclusters which served as a sintering aid during the heating process. However, increase of sintering temperature and time destroyed densification and conductivity of the sintered film containing the modified particles.

Robust Design of a Particle-Free Silver-Organo-Complex Ink with High Conductivity and Inkjet Stability for Flexible Electronics.

PubMed

Vaseem, Mohammad; McKerricher, Garret; Shamim, Atif

2016-01-13

Currently, silver-nanoparticle-based inkjet ink is commercially available. This type of ink has several serious problems such as a complex synthesis protocol, high cost, high sintering temperatures (∼200 °C), particle aggregation, nozzle clogging, poor shelf life, and jetting instability. For the emerging field of printed electronics, these shortcomings in conductive inks are barriers for their widespread use in practical applications. Formulating particle-free silver inks has potential to solve these issues and requires careful design of the silver complexation. The ink complex must meet various requirements, such as in situ reduction, optimum viscosity, storage and jetting stability, smooth uniform sintered films, excellent adhesion, and high conductivity. This study presents a robust formulation of silver-organo-complex (SOC) ink, where complexing molecules act as reducing agents. The 17 wt % silver loaded ink was printed and sintered on a wide range of substrates with uniform surface morphology and excellent adhesion. The jetting stability was monitored for 5 months to confirm that the ink was robust and highly stable with consistent jetting performance. Radio frequency inductors, which are highly sensitive to metal quality, were demonstrated as a proof of concept on flexible PEN substrate. This is a major step toward producing high-quality electronic components with a robust inkjet printing process.

Nanocrystalline ceramic materials

DOEpatents

Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

1994-01-01

A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

Voltage-Induced Nonlinear Conduction Properties of Epoxy Resin/Micron-Silver Particles Composites

NASA Astrophysics Data System (ADS)

Qu, Zhaoming; Lu, Pin; Yuan, Yang; Wang, Qingguo

2018-01-01

The nonlinear conduction properties of epoxy resin (ER)/micron-silver particles (MP) composites were investigated. Under sufficient high intensity applied constant voltage, the obvious nonlinear conduction properties of the samples with volume fraction 25% were found. With increments in the voltage, the conductive switching effect was observed. The nonlinear conduction mechanism of the ER/MP composites under high applied voltages could be attributed to the electrical current conducted via discrete paths of conductive particles induced by the electric field. The test results show that the ER/MP composites with nonlinear conduction properties are of great potential application in electromagnetic protection of electron devices and systems.

Nanocrystalline ceramic materials

DOEpatents

Siegel, R.W.; Nieman, G.W.; Weertman, J.R.

1994-06-14

A method is disclosed for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material. 19 figs.

Effects of particle size and coating on toxicologic parameters, fecal elimination kinetics and tissue distribution of acutely ingested silver nanoparticles in a mouse model

PubMed Central

Bergin, Ingrid L.; Wilding, Laura A.; Morishita, Masako; Walacavage, Kim; Ault, Andrew P.; Axson, Jessica L.; Stark, Diana I.; Hashway, Sara A.; Capracotta, Sonja S.; Leroueil, Pascale R.; Maynard, Andrew D.; Philbert, Martin A.

2015-01-01

Consumer exposure to silver nanoparticles (AgNP) via ingestion can occur due to incorporation of AgNP into products such as food containers and dietary supplements. AgNP variations in size and coating may affect toxicity, elimination kinetics or tissue distribution. Here, we directly compared acute administration of AgNP of two differing coatings and sizes to mice, using doses of 0.1, 1 and 10 mg/kg body weight/day administered by oral gavage for 3 days. The maximal dose is equivalent to 2000× the EPA oral reference dose. Silver acetate at the same doses was used as ionic silver control. We found no toxicity and no significant tissue accumulation. Additionally, no toxicity was seen when AgNP were dosed concurrently with a broad-spectrum antibiotic. Between 70.5% and 98.6% of the administered silver dose was recovered in feces and particle size and coating differences did not significantly influence fecal silver. Peak fecal silver was detected between 6- and 9-h post-administration and <0.5% of the administered dose was cumulatively detected in liver, spleen, intestines or urine at 48 h. Although particle size and coating did not affect tissue accumulation, silver was detected in liver, spleen and kidney of mice administered ionic silver at marginally higher levels than those administered AgNP, suggesting that silver ion may be more bioavailable. Our results suggest that, irrespective of particle size and coating, acute oral exposure to AgNP at doses relevant to potential human exposure is associated with predominantly fecal elimination and is not associated with accumulation in tissue or toxicity. PMID:26305411

Shock-induced microstructural response of mono- and nanocrystalline SiC ceramics

NASA Astrophysics Data System (ADS)

Branicio, Paulo S.; Zhang, Jingyun; Rino, José P.; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya

2018-04-01

The dynamic behavior of mono- and nanocrystalline SiC ceramics under plane shock loading is revealed using molecular-dynamics simulations. The generation of shock-induced elastic compression, plastic deformation, and structural phase transformation is characterized at different crystallographic directions as well as on a 5-nm grain size nanostructure at 10 K and 300 K. Shock profiles are calculated in a wide range of particle velocities 0.1-6.0 km/s. The predicted Hugoniot agree well with experimental data. Results indicate the generation of elastic waves for particle velocities below 0.8-1.9 km/s, depending on the crystallographic direction. In the intermediate range of particle velocities between 2 and 5 km/s, the shock wave splits into an elastic precursor and a zinc blende-to-rock salt structural transformation wave, which is triggered by shock pressure over the ˜90 GPa threshold value. A plastic wave, with a strong deformation twinning component, is generated ahead of the transformation wave for shocks in the velocity range between 1.5 and 3 km/s. For particle velocities greater than 5-6 km/s, a single overdriven transformation wave is generated. Surprisingly, shocks on the nanocrystalline sample reveal the absence of wave splitting, and elastic, plastic, and transformation wave components are seamlessly connected as the shock strength is continuously increased. The calculated strengths 15.2, 31.4, and 30.9 GPa for ⟨001⟩, ⟨111⟩, and ⟨110⟩ directions and 12.3 GPa for the nanocrystalline sample at the Hugoniot elastic limit are in excellent agreement with experimental data.

Mechanism of Particle Formation in Silver/Epoxy Nanocomposites Obtained through a Visible-Light-Assisted in Situ Synthesis.

PubMed

dell'Erba, Ignacio E; Martínez, Francisco D; Hoppe, Cristina E; Eliçabe, Guillermo E; Ceolín, Marcelo; Zucchi, Ileana A; Schroeder, Walter F

2017-10-03

A detailed understanding of the processes taking place during the in situ synthesis of metal/polymer nanocomposites is crucial to manipulate the shape and size of nanoparticles (NPs) with a high level of control. In this paper, we report an in-depth time-resolved analysis of the particle formation process in silver/epoxy nanocomposites obtained through a visible-light-assisted in situ synthesis. The selected epoxy monomer was based on diglycidyl ether of bisphenol A, which undergoes relatively slow cationic ring-opening polymerization. This feature allowed us to access a full description of the formation process of silver NPs before this was arrested by the curing of the epoxy matrix. In situ time-resolved small-angle X-ray scattering investigation was carried out to follow the evolution of the number and size of the silver NPs as a function of irradiation time, whereas rheological experiments combined with near-infrared and ultraviolet-visible spectroscopies were performed to interpret how changes in the rheological properties of the matrix affect the nucleation and growth of particles. The analysis of the obtained results allowed us to propose consistent mechanisms for the formation of metal/polymer nanocomposites obtained by light-assisted one-pot synthesis. Finally, the effect of a thermal postcuring treatment of the epoxy matrix on the particle size in the nanocomposite was investigated.

Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode.

PubMed

Farahi, Abdelfettah; Achak, Mounia; El Gaini, Laila; El Mhammedi, Moulay Abderrahim; Bakasse, Mina

2015-09-01

Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10 -7  mol/L to 1.0 × 10 -3  mol/L. The detection limit and quantification limit were 2.01 × 10 -8  mol/L and 6.073 × 10 -8  mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10 -5  mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures. Copyright © 2015. Published by Elsevier B.V.

Oral toxicity of silver ions, silver nanoparticles and colloidal silver--a review.

PubMed

Hadrup, Niels; Lam, Henrik R

2014-02-01

Orally administered silver has been described to be absorbed in a range of 0.4-18% in mammals with a human value of 18%. Based on findings in animals, silver seems to be distributed to all of the organs investigated, with the highest levels being observed in the intestine and stomach. In the skin, silver induces a blue-grey discoloration termed argyria. Excretion occurs via the bile and urine. The following dose-dependent animal toxicity findings have been reported: death, weight loss, hypoactivity, altered neurotransmitter levels, altered liver enzymes, altered blood values, enlarged hearts and immunological effects. Substantial evidence exists suggesting that the effects induced by particulate silver are mediated via silver ions that are released from the particle surface. With the current data regarding toxicity and average human dietary exposure, a Margin of Safety calculation indicates at least a factor of five before a level of concern to the general population is reached. Copyright © 2013 Elsevier Inc. All rights reserved.

Micromorphological characterization of zinc/silver particle composite coatings.

PubMed

Méndez, Alia; Reyes, Yolanda; Trejo, Gabriel; StĘpień, Krzysztof; Ţălu, Ştefan

2015-12-01

The aim of this study was to evaluate the three-dimensional (3D) surface micromorphology of zinc/silver particles (Zn/AgPs) composite coatings with antibacterial activity prepared using an electrodeposition technique. These 3D nanostructures were investigated over square areas of 5 μm × 5 μm by atomic force microscopy (AFM), fractal, and wavelet analysis. The fractal analysis of 3D surface roughness revealed that (Zn/AgPs) composite coatings have fractal geometry. Triangulation method, based on the linear interpolation type, applied for AFM data was employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The surface fractal dimension Df , as well as height values distribution have been determined for the 3D nanostructure surfaces. © 2015 The Authors published by Wiley Periodicals, Inc.

In vitro cytotoxity of silver: implication for clinical wound care.

PubMed

Poon, Vincent K M; Burd, Andrew

2004-03-01

In this study, we look at the cytotoxic effects of silver on keratinocytes and fibroblasts. We have assessed the viability of monolayer cultures using the MTT and BrdU assays. The composition of the culture medium and also the culture technique were modified to assess the effects of culture 'environment' on the susceptibility of the cells to the toxic action of silver. Further in vitro, experiments were performed using tissue culture models to allow cellular behavior in three dimensional planes which more closely simulated in vivo behavior. The silver source was both silver released from silver nitrate solution but also nanocrystalline silver released from a commercially available dressing. The results show that silver is highly toxic to both keratinocytes and fibroblasts in monolayer culture. When using optimized and individualized culture the fibroblasts appear to be more sensitive to silver than keratinocytes. However, when both cell types were grown in the same medium their viability was the same. Using tissue culture models again indicated an 'environmental effect' with decreased sensitivity of the cells to the cytotoxic effects of the silver. Nevertheless in these studies the toxic dose of skin cells ranging from 7 x 10(-4) to 55 x 10(-4)% was similar to that of bacteria. These results suggest that consideration of the cytotoxic effects of silver and silver-based products should be taken when deciding on dressings for specific wound care strategies. This is important when using keratinocyte culture, in situ, which is playing an increasing role in contemporary wound and burn care.

Development of CMC hydrogels loaded with silver nano-particles for medical applications.

PubMed

Hebeish, Ali; Hashem, M; El-Hady, M M Abd; Sharaf, S

2013-01-30

Innovative CMC-based hydrogels with great potentials for usage in medical area were principally synthesized as per two strategies .The first involved reaction of epichlorohydrin in alkaline medium containing silver nitrate to yield silver nano-particles (AgNPs)-loaded CMC hydrogel. While CMC acted as stabilizing for AgNPs, trisodium citrate was added to the reaction medium to assist CMC in establishing reduction of Ag(+) to AgNPs. The second strategy entailed preparation of CMC hydrogel which assists the in situ preparation of AgNPs under the same conditions. In both strategies, factors affecting the characterization of AgNPs-loaded CMC hydrogels were studied. Analysis and characterization of the so obtained hydrogels were performed through monitoring swelling behavior, FTIR spectroscopy, SEM, EDX, UV-vis spectrophotometer and TEM. Antimicrobial activity of the hydrogels was examined and mechanisms involved in their synthesis were reported. Copyright © 2012 Elsevier Ltd. All rights reserved.

Mechanical properties of nanocrystalline cobalt

NASA Astrophysics Data System (ADS)

Karimpoor, Amir A.; Erb, Uwe

2006-05-01

Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

[Raman studies of nanocrystalline BaTiO3 ceramics].

PubMed

Xiao, Chang-jiang; Jin, Chang-qing; Wang, Xiao-hui

2008-12-01

High pressure can significantly increase the densification. Further, during the high pressure assisted sintering, the nucleation rate is increased due to reduced energy barrier and the growth rate is suppressed due to the decreased diffusivity. Thus high pressure enables the specimen to be fabricated with relatively lower temperature and shorter sintering period that assures to obtain dense nanocrystalline ceramics. Dense nanocrystalline BaTiO3 ceramics with uniform grain sizes of 60 and 30 nm, respectively, were obtained by pressure assisted sintering. The crystal structure and phase transitions were investigated by Raman scattering at temperatures ranging from -190 to 200 degrees C. The Raman results indicated that the evolution of Raman spectrum with grain size is characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. With increasing temperature, similar to 3 mm BaTiO3 normal ceramics, the successive phase transitions from rhombohedral to orthorhombic, orthorhombic to tetragonal, and tetragonal to cubic were also observed in nanocrystalline BaTiO3 ceramics. In addition, when particle size is reduced to the nanoscale, one will find some unusual physical properties in nanocrystalline ceramics, compared with those of coarse-grained BaTiO3 ceramics. The different coexistences of multiphase were found at different temperature. Especially, the ferroelectric tetragonal and orthorhombic phase can coexist at room temperature in nanocrystalline BaTiO3 ceramics. The phenomenon can be explained by the internal stress. The coexistences of different ferroelectric phases at room temperature indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm.

Synthesis of nanocrystalline TiO 2 in toluene by a solvothermal route

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Tae Chung, Su; Son, Se-Mo

2003-07-01

A solvothermal synthetic method to TiO 2 nanoparticles has been investigated in toluene solutions with titanium isopropoxide (TIP) as precursor. Weight ratios of precursor to solvent prepared in the mixture are 5/100, 10/100, 20/100, 30/100 and 40/100. At the weight ratio of 10/100, 20/100 and 30/100, TiO 2 nanocrystalline particles were obtained after synthesis at 250°C for 3 h in an autoclave. X-ray diffraction and tranmission electron microscopy shows that the product has uniform anatase structure with average particle size below 20 nm. As the composition of TIP in the solution increases, the particle size of TiO 2 powder tends to increase. At 5/100 and 40/100, however, pale yellow colloidal solution is obtained after synthesis and crystalline phase of TiO 2 is not produced. The specific surface area of the TiO 2 nanocrystalline powder was also investigated using BET surface area analyzer.

Preparation of silver nanoparticles at low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Mini, E-mail: mishramini5@gmail.com; Chauhan, Pratima, E-mail: mangu167@yahoo.co.in

Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaksmore » of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.« less

Effect of ultrasonic treatment and temperature on nanocrystalline TiO 2

NASA Astrophysics Data System (ADS)

Kim, D. H.; Ryu, H. W.; Moon, J. H.; Kim, J.

Nanocrystalline TiO 2 particles were precipitated from the ethanol solution of titanium isopropoxide (Ti(O- iPr) 4) and H 2O 2 by refluxing at 80 °C for 48 h. The obtained particles were filtered and dried at 100 °C for 12 h. The dried powder itself, the sample with heating at 400 °C, and the sample with ultrasonically treating were prepared to investigate the effects of post treatments on materials characteristics and electrochemical properties of nanocrystalline TiO 2. The X-ray diffraction patterns of all of the samples were fitted well to the anatase phase. The field emission-TEM image of as-prepared sample shows a uniform spherical morphology with 5 nm particle size and the sample heated at 400 °C shows slightly increased particle size of about 10 nm while maintaining spherical shape. The sample treated with ultrasonic for 5 h or more at room temperature shows high aspect ratio particle shape with an average diameter of 5 nm and a length of 20 nm. According to the results of the electrochemical testing, as-prepared sample, the sample heated at 400 °C for 3 h, and the sample treated with ultrasonic show initial capacities of 270, 310 and 340 mAh g -1, respectively.

Silver, bighead, and common carp orient to acoustic particle motion when avoiding a complex sound.

PubMed

Zielinski, Daniel P; Sorensen, Peter W

2017-01-01

Behavioral responses of silver carp (Hypopthalmichthys molitrix), bighead carp (H. nobilis), and common carp (Cyprinus carpio) to a complex, broadband sound were tested in the absence of visual cues to determine whether these species are negatively phonotaxic and the roles that sound pressure and particle motion might play mediating this response. In a dark featureless square enclosure, groups of 3 fish were tracked and the distance of each fish from speakers and their swimming trajectories relative to sound pressure and particle acceleration were analyzed before, and then while an outboard motor sound was played. All three species exhibited negative phonotaxis during the first two exposures after which they ceased responding. The median percent time fish spent near the active speaker for the first two trials decreased from 7.0% to 1.3% for silver carp, 7.9% to 1.1% for bighead carp, and 9.5% to 3% for common carp. Notably, when close to the active speaker fish swam away from the source and maintained a nearly perfect 0° orientation to the axes of particle acceleration. Fish did not enter sound fields greater than 140 dB (ref. 1 μPa). These results demonstrate that carp avoid complex sounds in darkness and while initial responses may be informed by sound pressure, sustained oriented avoidance behavior is likely mediated by particle motion. This understanding of how invasive carp use particle motion to guide avoidance could be used to design new acoustic deterrents to divert them in dark, turbid river waters.

Silver, bighead, and common carp orient to acoustic particle motion when avoiding a complex sound

PubMed Central

Sorensen, Peter W.

2017-01-01

Behavioral responses of silver carp (Hypopthalmichthys molitrix), bighead carp (H. nobilis), and common carp (Cyprinus carpio) to a complex, broadband sound were tested in the absence of visual cues to determine whether these species are negatively phonotaxic and the roles that sound pressure and particle motion might play mediating this response. In a dark featureless square enclosure, groups of 3 fish were tracked and the distance of each fish from speakers and their swimming trajectories relative to sound pressure and particle acceleration were analyzed before, and then while an outboard motor sound was played. All three species exhibited negative phonotaxis during the first two exposures after which they ceased responding. The median percent time fish spent near the active speaker for the first two trials decreased from 7.0% to 1.3% for silver carp, 7.9% to 1.1% for bighead carp, and 9.5% to 3% for common carp. Notably, when close to the active speaker fish swam away from the source and maintained a nearly perfect 0° orientation to the axes of particle acceleration. Fish did not enter sound fields greater than 140 dB (ref. 1 μPa). These results demonstrate that carp avoid complex sounds in darkness and while initial responses may be informed by sound pressure, sustained oriented avoidance behavior is likely mediated by particle motion. This understanding of how invasive carp use particle motion to guide avoidance could be used to design new acoustic deterrents to divert them in dark, turbid river waters. PMID:28654676

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

PubMed

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

2016-10-20

Immobilized silver nano-particles (Ag NPs) possess excellent antimicrobial properties due to their unique surface characteristics. In this paper, immobilized silver nano-particles were synthesized in the presence of chitin nano-crystals (CNC) based on the Tollens mechanism (reduction of silver ion by aldehydes in the chitosan oligosaccharides (COS)) under microwave-assisted conditions. The prepared Ag NPs-loaded CNC nano-composites were then applied onto the paper surface via coating for the preparation of antibacterial paper. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results confirmed that the Ag NPs were immobilized onto the CNC. The transmission electron microscope (TEM) and scanning electron microscopy (SEM) results further revealed that the spherical Ag NPs (5-12nm) were well dispersed on the surface of CNC. The coated paper made from the Ag NPs-loaded CNC nano-composites exhibited a high effectiveness of the antibacterial activity against E. coli or S. aureus. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis of silver nanoparticles by endosymbiont Pseudomonas fluorescens CA 417 and their bactericidal activity.

PubMed

Syed, Baker; M N, Nagendra Prasad; B L, Dhananjaya; K, Mohan Kumar; S, Yallappa; S, Satish

2016-12-01

The present study emphasizes on biogenic synthesis of silver nanoparticles and their bactericidal activity against human and phytopathogens. Nanoparticle synthesis was performed using endosymbiont Pseudomonas fluorescens CA 417 inhabiting Coffea arabica L. Synthesized nanoparticles were characterized using hyphenated spectroscopic techniques such as UV-vis spectroscopy which revealed maximum absorption 425nm. Fourier transform infrared spectroscopy (FTIR) analysis revealed the possible functional groups mediating and stabilizing silver nanoparticles with predominant peaks occurring at 3346 corresponding to hydroxyl group, 1635 corresponding carbonyl group and 680 to aromatic group. X-ray diffraction (XRD) analysis revealed the Bragg's diffraction pattern with distinct peaks at 38° 44°, 64° and 78° revealing the face-centered cubic (fcc) metallic crystal corresponding to the (111), (200), (220) and (311) facets of the crystal planes at 2θ angle. The energy dispersive X-ray spectroscopy (EDS) analysis revealed presence of high intense absorption peak at 3keV is a typical characteristic of nano-crystalline silver which confirmed the presence of elemental silver. TEM analysis revealed the size of the nanoparticles to be in the range 5-50nm with polydisperse nature of synthesized nanoparticles bearing myriad shapes. The particle size determined by Dynamic light scattering (DLS) method revealed average size to be 20.66nm. The synthesized silver nanoparticles exhibited significant antibacterial activity against panel of test pathogens. The results showed Klebsiella pneumoniae (MTCC 7407) and Xanthomonas campestris to be more sensitive among the test human pathogen and phyto-pathogen respectively. The study also reports synergistic effect of silver nanoparticles in combination with kanamycin which displayed increased fold activity up to 58.3% against Klebsiella pneumoniae (MTCC 7407). The results of the present investigation are promising enough and attribute towards

Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

PubMed

Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

2011-01-01

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.

Micromorphological characterization of zinc/silver particle composite coatings

PubMed Central

Méndez, Alia; Reyes, Yolanda; Trejo, Gabriel; StĘpień, Krzysztof

2015-01-01

ABSTRACT The aim of this study was to evaluate the three‐dimensional (3D) surface micromorphology of zinc/silver particles (Zn/AgPs) composite coatings with antibacterial activity prepared using an electrodeposition technique. These 3D nanostructures were investigated over square areas of 5 μm × 5 μm by atomic force microscopy (AFM), fractal, and wavelet analysis. The fractal analysis of 3D surface roughness revealed that (Zn/AgPs) composite coatings have fractal geometry. Triangulation method, based on the linear interpolation type, applied for AFM data was employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The surface fractal dimension D f, as well as height values distribution have been determined for the 3D nanostructure surfaces. Microsc. Res. Tech. 78:1082–1089, 2015. © 2015 The Authors published by Wiley Periodicals, Inc. PMID:26500164

The role of silver nano-particles and silver thiosulfate on the longevity of cut carnation (Dianthus caryophyllus) flowers.

PubMed

Hashemabadi, Davood

2014-07-01

The purpose of this study was to evaluate the efficacy of silver nano-particles (SNP) and silver thiosulfate (STS) in extending the vase life of cut carnation (Dianthus caryophyllus L. cv. 'Tempo') flowers. Pulse treatments of SNP @ 0, 5, 10 and 15 mg l(-1) and STS @ 0, 0.1, 0.2 and 0.3 mM were administered to carnation flowers for 24 hr. The longest vase life (16.1 days) was observed in flowers treated with 15 mg l(-1) of SNP + 0.2 mM STS. The least chlorophyll was destroyed in flowers treated with 15 mg I(-1) of SNP + 0.3 mM STS. Our findings showed that the 15 mg l(-1) SNP treatment inhibited bacterial growth in the preservative solution. The control flowers bloomed faster than the treated flowers. The maximum peroxidase activity and the minimum lipid peroxidation were obtained in cut flowers that were treated with 15 mg l(-1) of SNP and 0.3 mM STS. Overall, results of the study revealed that SNP and STS treatment extended the longevity of cut carnation 'Tempo' flowers by reducing oxidative stress, improving anti-oxidant system, reducing bacterial populations and delaying flowering.

A Study on the Plasmonic Properties of Silver Core Gold Shell Nanoparticles: Optical Assessment of the Particle Structure

NASA Astrophysics Data System (ADS)

Mott, Derrick; Lee, JaeDong; Thi Bich Thuy, Nguyen; Aoki, Yoshiya; Singh, Prerna; Maenosono, Shinya

2011-06-01

This paper reports a qualitative comparison between the optical properties of a set of silver core, gold shell nanoparticles with varying composition and structure to those calculated using the Mie solution. To achieve this, silver nanoparticles were synthesized in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing-capping agent. The particles were then coated with a layer of gold with controllable thickness through a reduction-deposition process. The resulting nanoparticles reveal well defined optical properties that make them suitable for comparison to ideal calculated results using the Mie solution. The discussion focuses on the correlation between the synthesized core shell nanoparticles with varying Au shell thickness and the Mie solution results in terms of the optical properties. The results give insight in how to design and synthesize silver core, gold shell nanoparticles with controllable optical properties (e.g., SPR band in terms of intensity and position), and has implications in creating nanoparticle materials to be used as biological probes and sensing elements.

Characterization of engineered nanoparticles in commercially available spray disinfectant products advertised to contain colloidal silver.

PubMed

Rogers, Kim R; Navratilova, Jana; Stefaniak, Aleksandr; Bowers, Lauren; Knepp, Alycia K; Al-Abed, Souhail R; Potter, Phillip; Gitipour, Alireza; Radwan, Islam; Nelson, Clay; Bradham, Karen D

2018-04-01

Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characterization parameters included: total silver, fractionated silver (particulate and dissolved), primary particle size distribution, hydrodynamic diameter, particle number, and plasmon resonance absorbance. A high degree of variability between claimed and measured values for total silver was observed. Only 7 of the products showed total silver concentrations within 20% of their nominally reported values. In addition, significant variations in the relative percentages of particulate vs. soluble silver were also measured in many of these products reporting to be colloidal. Primary silver particle size distributions by transmission electron microscopy (TEM) showed two populations of particles - smaller particles (<5nm) and larger particles between 20 and 40nm. Hydrodynamic diameter measurements using nanoparticle tracking analysis (NTA) correlated well with TEM analysis for the larger particles. Z-average (Z-Avg) values measured using dynamic light scattering (DLS); however, were typically larger than both NTA or TEM particle diameters. Plasmon resonance absorbance signatures (peak absorbance at around 400nm indicative of metallic silver nanoparticles) were only noted in 4 of the 9 yellow-brown colored suspensions. Although the total silver concentrations were variable among products, ranging from 0.54mg/L to 960mg/L, silver containing nanoparticles were identified in all of the product suspensions by TEM. Published by Elsevier B.V.

Size Selective Green Synthesis of Silver and Gold Nanoparticles: Enhanced Antibacterial Efficacy of Resveratrol Capped Silver Sol.

PubMed

Shukla, Shashi P; Roy, Mainak; Mukherjee, Poulomi; Das, Laboni; Neogy, Suman; Srivastava, Dinesh; Adhikari, Soumyakanti

2016-03-01

In view of potential biomedical application of the noble metal nanoparticles, we report a size controlled yet simple and green synthesis of resveratrol stabilized silver and gold nanoparticles having low polydispersity of size. Here, resveratrol plays two simultaneous roles, reducing the metal ions and providing efficient capping of the small nanoparticles. This gives rise to specific size of silver and gold nanoparticles at specific ratios of metal to resveratrol. The particles have been characterized by XRD and transmission electron microscopy. The nanoparticle sols are stable for months. The UV Visible absorption spectra of the silver sol show the plasmon peak of spherical nanoparticles, presence of which is further reflected in the TEM images. Size of the silver particles obtained is in between 11 to 21 nm depending on the ratio of resveratrol to metal ion used. Resveratrol capped silver nanoparticles exhibit high antibacterial activity against Gram negative wild type E coli BW (25113). The minimum inhibitory concentration (MIC) of nano-silver against the bacterium has been estimated to be 6.48 μg/ml, which is significantly lower than that reported in some earlier as well as recent publications. Reaction of gold ions with resveratrol, on the other hand, produces gold nanoparticles of sizes varying from 7 to 29 nm at different ratios of resveratrol to the metal ions. Particles with higher size and aspect ratio are formed at lower concentration of the capping agent whereas particles with very small size and pseudo-spherical morphology are formed at higher capping concentration. Difference in the formation kinetics of silver and gold nanoparticles has been attributed to the different growth mechanisms in the two cases. Possible modes of anchorage of resveratrol to silver nanoparticles have been investigated using surface enhanced resonance Raman spectroscopy (SERS) which shows that the silver nanoparticles are capped by resveratrol molecule primarily through O

Contaminant degradation by irradiated semiconducting silver chloride particles: kinetics and modelling.

PubMed

Ma, Tian; Garg, Shikha; Miller, Christopher J; Waite, T David

2015-05-15

The kinetics and mechanism of light-mediated formic acid (HCOO(-)) degradation in the presence of semiconducting silver chloride particles are investigated in this study. Our experimental results show that visible-light irradiation of AgCl(s) results in generation of holes and electrons with the photo-generated holes and its initial oxidation product carbonate radical, oxidizing HCOO(-) to form CO2. The HCOO(-) degradation rate increases with increase in silver concentration due to increase in rate of photo-generation of holes while the increase in chloride concentration decreases the degradation rate of HCOO(-) as a result of the scavenging of holes by Cl(-), thereby resulting in decreased holes and carbonate radical concentration. The results obtained indicate that a variety of other solution conditions including dioxygen concentration, bicarbonate concentration and pH influence the availability of holes and hence the HCOO(-) degradation rate in a manner consistent with our understanding of key processes. Based on our experimental results, we have developed a kinetic model capable of predicting AgCl(s)-mediated HCOO(-) photo-degradation over a wide range of conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

Biologically inspired rosette nanotubes and nanocrystalline hydroxyapatite hydrogel nanocomposites as improved bone substitutes

NASA Astrophysics Data System (ADS)

Zhang, Lijie; Rodriguez, Jose; Raez, Jose; Myles, Andrew J.; Fenniri, Hicham; Webster, Thomas J.

2009-04-01

Today, bone diseases such as bone fractures, osteoporosis and bone cancer represent a common and significant public health problem. The design of biomimetic bone tissue engineering materials that could restore and improve damaged bone tissues provides exciting opportunities to solve the numerous problems associated with traditional orthopedic implants. Therefore, the objective of this in vitro study was to create a biomimetic orthopedic hydrogel nanocomposite based on the self-assembly properties of helical rosette nanotubes (HRNs), the osteoconductive properties of nanocrystalline hydroxyapatite (HA), and the biocompatible properties of hydrogels (specifically, poly(2-hydroxyethyl methacrylate), pHEMA). HRNs are self-assembled nanomaterials that are formed from synthetic DNA base analogs in water to mimic the helical nanostructure of collagen in bone. In this study, different geometries of nanocrystalline HA were controlled by either hydrothermal or sintering methods. 2 and 10 wt% nanocrystalline HA particles were well dispersed into HRN hydrogels using ultrasonication. The nanocrystalline HA and nanocrystalline HA/HRN hydrogels were characterized by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Mechanical testing studies revealed that the well dispersed nanocrystalline HA in HRN hydrogels possessed improved mechanical properties compared to hydrogel controls. In addition, the results of this study provided the first evidence that the combination of either 2 or 10 wt% nanocrystalline HA and 0.01 mg ml-1 HRNs in hydrogels greatly increased osteoblast (bone-forming cell) adhesion up to 236% compared to hydrogel controls. Moreover, this study showed that HRNs stimulated HA nucleation and mineralization along their main axis in a way that is very reminiscent of the HA/collagen assembly pattern in natural bone. In summary, the presently observed excellent properties of the biomimetic nanocrystalline HA/HRN hydrogel composites

Characterization of Electrochemically Generated Silver

NASA Technical Reports Server (NTRS)

Adam, Niklas; Martinez, James; Carrier, Chris

2014-01-01

Silver biocide offers a potential advantage over iodine, the current state of the art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. Low concentrations of silver (<500 ppb) have been shown to kill bacteria in water systems and keep it safe for potability. Silver does not require hardware to remove it from a water system, and therefore can provide a simpler means for disinfecting water. The Russian segment of the International Space Station has utilized an electrochemically generated silver solution, which is colloidal in nature. To be able to reliably provide a silver biocide to drinking water by electrochemical means would reduce mass required for removing another biocide such as iodine from the water. This would also aid in crew time required to replace iodine removal cartridges. Future long term missions would benefit from electrochemically produced silver as the biocide could be produced on demand and requires only a small concentration to be effective. Since it can also be consumed safely, there is less mass in removal hardware and little consumables required for production. The goal of this project initially is to understand the nature of the electrochemically produced silver, the particle sizes produced by the electrochemical cell and the effect that voltage adjustment has on the particle size. In literature, it has been documented that dissolved oxygen and pH have an effect on the ionization of the electrochemical silver so those parameters would be measured and possibly adjusted to understand their effect on the silver.

A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles

PubMed Central

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

2013-01-01

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. PMID:24039420

Silver Ink For Jet Printing

NASA Technical Reports Server (NTRS)

Vest, R. W.; Singaram, Saraswathi

1989-01-01

Metallo-organic ink containing silver (with some bismuth as adhesion agent) applied to printed-circuit boards and pyrolized in air to form electrically conductive patterns. Ink contains no particles of silver, does not have to be mixed during use to maintain homogeneity, and applied to boards by ink-jet printing heads. Consists of silver neodecanoate and bismuth 2-ethylhexanoate dissolved in xylene and/or toluene.

Fabricating the spherical and flake silver powder used for the optoelectronic devices

NASA Astrophysics Data System (ADS)

Ju, Wei; Ma, Wangjing; Zhang, Fangzhi; Chen, Yixiang; Xie, Jinpeng

2018-01-01

The spherical and flake silver powder with different particle size for the optoelectronic devices was partly prepared by using chemical reduction and ball milling method, and charactered by scanning electron microscope (SEM), X-ray diffraction (XRD), laser particle size analyzer and thermo-gravimetric(TG) analyzer. The particle size of three series of spherical silver powder fabricated by chemical reduction is about 1.5μm, 1μm and 0.6μm, respectively; after being mechanical milling, the particle size of flake silver powder with high flaky rate is about 10μm, 6μm and 2μm respectively. Thermo gravimetric (TG) and XRD analyses showed that the silver powders have high purity and crystalline, and then the laser particle size and SEM analyses showed that the silver powders has good uniformity.

Effects of different operating parameters on the particle size of silver chloride nanoparticles prepared in a spinning disk reactor

NASA Astrophysics Data System (ADS)

Dabir, Hossein; Davarpanah, Morteza; Ahmadpour, Ali

2015-07-01

The aim of this research was to present an experimental method for large-scale production of silver chloride nanoparticles using spinning disk reactor. Silver nitrate and sodium chloride were used as the reactants, and the protecting agent was gelatin. The experiments were carried out in a continuous mode by injecting the reactants onto the surface of the spinning disk, where a chemical precipitation reaction took place to form AgCl particles. The effects of various operating variables, including supersaturation, disk rotational speed, reactants flow rate, disk diameter, and excess ions, on the particle size of products were investigated. In addition, the AgCl nanoparticles were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. According to the results, smaller AgCl particles are obtained under higher supersaturations and also higher disk rotation speeds. Moreover, in the range of our investigation, the use of lower reactants flow rates and larger disk diameter can reduce the particle size of products. The non-stoichiometric condition of reactants has a significant influence on the reduction in particle aggregation. It was also found that by optimizing the operating conditions, uniform AgCl nanoparticles with the mean size of around 37 nm can be produced.

Superparamagnetic nanocrystalline ZnFe2O4 with a very high Curie temperature.

PubMed

Deka, Sasanka; Joy, P A

2008-08-01

Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as approximately 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.

Rate Dependency of Silver Vanadium Phosphorous Oxide Reduction

NASA Astrophysics Data System (ADS)

Cheng, Po-Jen

2011-12-01

The silver vanadium phosphorus oxide (Ag2VO2PO 4) is a high-capacity and good-compatibility material for the cathode in the battery. Due to their innovative properties, they are used as cathode in lithium batteries. Therefore, when the lithium batteries begin to discharge, the anodes of the cell perform an electrochemical oxidation and release electrons. In the mean time, the cathodes in the cells perform the electrochemical reduction and catch the electrons. For reduction of Ag2VO2PO 4, two silver ions (Ag+) catch two electrons to form silver particles, and the vanadium ions (V5+) catch two electrons to form V3+. It means that four electrons will be released by lithium anode. We call this four electrons discharge as 100% discharge. In my most of the projects, the Ag2VO2PO4 material is tested by differential scanning calorimetry (DSC) to check purity. My study is based on the discharge of batteries, and I focus on the morphology and the intensity of silver particles on the cathode after discharge. Depending on different adjustment of factors, such as discharge time, discharge rate, storage time, storage temperature, I try to investigate the silver intensity, conductivity as a function of DOD (Depth of Discharge). The silver particles could be examined by optical microscope, and scanning electron microscope (SEM). Moreover, I do some x-ray diffraction analysis to quantify the silver particles after discharge. Also, I perform magnetic susceptibility measurement to check the mechanism of the reduction of vanadium ions. Under the research on silver ions and vanadium ions, I will know a big frame of reduction process on silver vanadium phosphorous oxide and the time effect on this cathode material.

One-Pot Silver Nanoring Synthesis

NASA Astrophysics Data System (ADS)

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2010-03-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-pot silver nanoring synthesis.

PubMed

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2009-12-16

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-Pot Silver Nanoring Synthesis

PubMed Central

2010-01-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV–vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation. PMID:20672109

Method to grow pure nanocrystalline diamond films at low temperatures and high deposition rates

DOEpatents

Carlisle, John A [Plainfield, IL; Gruen, Dieter M [Downers Grove, IL; Auciello, Orlando [Bolingbrook, IL; Xiao, Xingcheng [Woodridge, IL

2009-07-07

A method of depositing nanocrystalline diamond film on a substrate at a rate of not less than about 0.2 microns/hour at a substrate temperature less than about 500.degree. C. The method includes seeding the substrate surface with nanocrystalline diamond powder to an areal density of not less than about 10.sup.10sites/cm.sup.2, and contacting the seeded substrate surface with a gas of about 99% by volume of an inert gas other than helium and about 1% by volume of methane or hydrogen and one or more of acetylene, fullerene and anthracene in the presence of a microwave induced plasma while maintaining the substrate temperature less than about 500.degree. C. to deposit nanocrystalline diamond on the seeded substrate surface at a rate not less than about 0.2 microns/hour. Coatings of nanocrystalline diamond with average particle diameters of less than about 20 nanometers can be deposited with thermal budgets of 500.degree. C.-4 hours or less onto a variety of substrates such as MEMS devices.

Imaging of Biological Cells Using Luminescent Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Kravets, Vira; Almemar, Zamavang; Jiang, Ke; Culhane, Kyle; Machado, Rosa; Hagen, Guy; Kotko, Andriy; Dmytruk, Igor; Spendier, Kathrin; Pinchuk, Anatoliy

2016-01-01

The application of luminescent silver nanoparticles as imaging agents for neural stem and rat basophilic leukemia cells was demonstrated. The experimental size dependence of the extinction and emission spectra for silver nanoparticles were also studied. The nanoparticles were functionalized with fluorescent glycine dimers. Spectral position of the resonance extinction and photoluminescence emission for particles with average diameters ranging from 9 to 32 nm were examined. As the particle size increased, the spectral peaks for both extinction and the intrinsic emission of silver nanoparticles shifted to the red end of the spectrum. The intrinsic photoluminescence of the particles was orders of magnitude weaker and was spectrally separated from the photoluminescence of the glycine dimer ligands. The spectral position of the ligand emission was independent of the particle size; however, the quantum yield of the nanoparticle-ligand system was size-dependent. This was attributed to the enhancement of the ligand's emission caused by the local electric field strength's dependence on the particle size. The maximum quantum yield determined for the nanoparticle-ligand complex was (5.2 ± 0.1) %. The nanoparticles were able to penetrate cell membranes of rat basophilic leukemia and neural stem cells fixed with paraformaldehyde. Additionally, toxicity studies were performed. It was found that towards rat basophilic leukemia cells, luminescent silver nanoparticles had a toxic effect in the silver atom concentration range of 10-100 μM.

Thermally Stable Nanocrystalline Steel

NASA Astrophysics Data System (ADS)

Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

2017-10-01

Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

Green Synthesis of Silver Nanoparticles by using Eucalyptus Globulus Leaf Extract

NASA Astrophysics Data System (ADS)

Balamurugan, Madheswaran; Saravanan, Shanmugam

2017-12-01

A single step eco-friendly, energy efficient and economically scalable green method was employed to synthesize silver nanoparticles. In this work, the synthesis of silver nanoparticles using Eucalyptus globulus leaf extract as reducing and capping agent along with water as solvent at normal room temperature is described. Silver nanoparticles were prepared from aqueous silver nitrate solution by adding the leaf extract. The prepared nanoparticles were characterized by using UV-visible Spectrophotometer, X-ray diffractometer, High Resolution Transmission Electron Microscope (HR-TEM) and Fourier Transform Infrared Spectroscope (FTIS). X-ray diffraction studies brought to light the crystalline nature and the face centered cubic structure of the silver nanoparticles. Using HR-TEM. the nano sizes and morphology of the particles were studied. The mean sizes of the prepared silver nanoparticles ranged from 30 to 36 nm. The density of the particles was tuned by varying the molar ratio of silver nitrate. FTIS studies showed the functional group of organic molecules which were located on the surface of the silver nanoparticles. Originating from the leaf extracts, these organic molecules reduced and capped the particles.

Synthesis of silver nanoparticles in melts of amphiphilic polyesters

NASA Astrophysics Data System (ADS)

Vasylyev, S.; Damm, C.; Segets, D.; Hanisch, M.; Taccardi, N.; Wasserscheid, P.; Peukert, W.

2013-03-01

The current work presents a one-step procedure for the synthesis of amphiphilic silver nanoparticles suitable for production of silver-filled polymeric materials. This solvent free synthesis via reduction of Tollens’ reagent as silver precursor in melts of amphiphilic polyesters consisting of hydrophilic poly(ethylene glycol) blocks and hydrophobic alkyl chains allows the production of silver nanoparticles without any by-product formation. This makes them especially interesting for the production of medical devices with antimicrobial properties. In this article the influences of the chain length of the hydrophobic block in the amphiphilic polyesters and the process temperature on the particle size distribution (PSD) and the stability of the particles against agglomeration are discussed. According to the results of spectroscopic and viscosimetric investigations the silver precursor is reduced to elemental silver nanoparticles by a single electron transfer process from the poly(ethylene glycol) chain to the silver ion.

Efficient Second-Harmonic Generation in Nanocrystalline Silicon Nanoparticles.

PubMed

Makarov, Sergey V; Petrov, Mihail I; Zywietz, Urs; Milichko, Valentin; Zuev, Dmitry; Lopanitsyna, Natalia; Kuksin, Alexey; Mukhin, Ivan; Zograf, George; Ubyivovk, Evgeniy; Smirnova, Daria A; Starikov, Sergey; Chichkov, Boris N; Kivshar, Yuri S

2017-05-10

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

Effect of silver nano particles on flexural strength of acrylic resins.

PubMed

Sodagar, Ahmad; Kassaee, Mohammad Zaman; Akhavan, Azam; Javadi, Negar; Arab, Sepideh; Kharazifard, Mohammad Javad

2012-04-01

Poly(methyl methacrylate), PMMA, is widely used for fabrication of removable orthodontic appliances. Silver nano particles (AgNps) have been added to PMMA because of their antimicrobial properties. The aim of this study is to investigate the effect of AgNps on the flexural strength of PMMA. Acrylic liquid containing 0.05% and 0.2% AgNps was prepared for two kinds of acrylic resins: Rapid Repair &Selecta Plus. Two groups without AgNps were used as control groups. For each one, flexural strength was investigated via Three Point Bending method for the 15 acrylic blocks. Two-way ANOVA, one way ANOVA and Tukey tests were used for statistical analysis. Rapid Repair without AgNps showed the highest flexural strength. Addition of 0.05% AgNps to Rapid Repair, significantly decreased its flexural strength while, continuing the addition up to 0.2% increased it nearly up to its primary level. In contrast, addition of AgNps to Selecta Plus increased its flexural strength but addition of 0.05% nano particles was more effective than 0.2%. The effect of AgNps on flexural strength of PMMA depends on several factors including the type of acrylics and the concentrations of nano particles. Copyright © 2011 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

3-dimensional free standing micro-structures by proton beam writing of Su 8-silver nanoParticle polymeric composite

NASA Astrophysics Data System (ADS)

Igbenehi, H.; Jiguet, S.

2012-09-01

Proton beam lithography a maskless direct-write lithographic technique (well suited for producing 3-Dimensional microstructures in a range of resist and semiconductor materials) is demonstrated as an effective tool in the creation of electrically conductive freestanding micro-structures in an Su 8 + Nano Silver polymer composite. The structures produced show non-ohmic conductivity and fit the percolation theory conduction model of tunneling of separated nanoparticles. Measurements show threshold switching and a change in conductivity of at least 4 orders of magnitude. The predictable range of protons in materials at a given energy is exploited in the creation of high aspect ratio, free standing micro-structures, made from a commercially available SU8 Silver nano-composite (GMC3060 form Gersteltec Inc. a negative tone photo-epoxy with added metallic nano-particles(Silver)) to create films with enhanced electrical properties when exposed and cured. Nano-composite films are directly written on with a finely focused MeV accelerated Proton particle beam. The energy loss of the incident proton beams in the target polymer nano- composite film is concentrated at the end of its range, where damage occurs; changing the chemistry of the nano-composite film via an acid initiated polymerization - creating conduction paths. Changing the energy of the incident beams provide exposed regions with different penetration and damage depth - exploited in the demonstrated cantilever microstructure.

Nanocrystalline NiNd0.01Fe1.99O4 as a gas sensor

NASA Astrophysics Data System (ADS)

Shinde, Tukaram J.; Gadkari, Ashok B.; Jadhav, Sarjerao R.; Kumar, Surender; Dalawai, Sanjeev P.; Vasambekar, Pramod N.

2015-06-01

Nanocrystalline NiNd0.01Fe1.99O4 has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl2, LPG and C2H5OH. It was observed that NiNd0.01Fe1.99O4 is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

Plant-mediated synthesis of silver nanoparticles using parsley ( Petroselinum crispum) leaf extract: spectral analysis of the particles and antibacterial study

NASA Astrophysics Data System (ADS)

Roy, Kaushik; Sarkar, C. K.; Ghosh, C. K.

2015-12-01

Synthesis of nanomaterials may involve various routes including physical, chemical and biological approaches. Here, the biological green route was chosen to prepare silver nanoparticles from silver salts to avoid the requirement of costly instruments and involvement of hazardous chemicals as well. To make the process clean and green, leaf extract of parsley ( Petroselinum crispum) was used to synthesize Ag nanoparticles at room temperature. The formation of Ag-nanoparticles was monitored by UV-Vis spectroscopy. The presence of silver in the sample and its crystalline nature were verified by X-ray diffraction (XRD) analysis. The size distribution profile and particle size in the suspension were manipulated from dynamic light scattering (DLS) pattern. The shape, size and morphology of the biogenic nanoparticles were studied using high resolution transmission electron microscope (TEM). Fourier transform infra-red spectroscopy was used to detect the biomolecules responsible for reduction of silver ions. These biogenic Ag-nanoparticles showed appreciable antibacterial efficacy against three bacteria— Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus.

Effect of silver thickness on structural, optical and morphological properties of nanocrystalline Ag/NiO thin films

NASA Astrophysics Data System (ADS)

Jalili, S.; Hajakbari, F.; Hojabri, A.

2018-03-01

Silver (Ag) nanolayers were deposited on nickel oxide (NiO) thin films by DC magnetron sputtering. The thickness of Ag layers was in range of 20-80 nm by variation of deposition time between 10 and 40 s. X-ray diffraction results showed that the crystalline properties of the Ag/NiO films improved by increasing the Ag film thickness. Also, atomic force microscopy and field emission scanning electron microscopy images demonstrated that the surface morphology of the films was highly affected by film thickness. The film thickness and the size of particles change by elevating the Ag deposition times. The composition of films was determined by Rutherford back scattering spectroscopy. The transmission of light was gradually reduced by augmentation of Ag films thickness. Furthermore; the optical band gap of the films was also calculated from the transmittance spectra.

Effect of silver nanoparticles on concentration of silver heavy element and growth indexes in cucumber ( Cucumis sativus L . negeen)

NASA Astrophysics Data System (ADS)

Shams, Gholamabbas; Ranjbar, Morteza; Amiri, Aliasghar

2013-05-01

The tremendous progress on nanoparticle research area has been made significant effects on the economy, society, and the environment. Silver nanoparticle is one of the most important particles in these categories. Silver nanoparticles can be converted to the heavy silver metal in water by oxidation. Moreover, in the high amounts of silver concentration, they will be accumulated in different parts of the plant. However, by changing the morphology of the plant, the production will be harmful for human consumptions. In this study, nano-powders with average 50 nm silver particles are mixed with deionized distilled water in a completely randomized design. Seven treatments with various concentrations of suspension silver nanoparticles were prepared and repeated in four different parts of the plant in a regular program of spraying. Samples were analyzed to study the growth indexes and concentration of silver in different parts of the plant. It was observed that with increasing concentration of silver nanoparticles on cucumber, the growth indexes (except pH fruit), and the concentration of silver heavy metal are increased significantly. The incremental concentration had the linear relationship with correlation coefficient 0.95 and an average of 0.617 PPM by increasing of each unit in one thousand concentration of nanosilver. Although, by increasing concentration of silver nanoparticles as spraying form, the plant morphological characteristics were improved, the concentration of silver heavy metal in various plant organs was increased. These results open a new pathway to consider the effect of nanoparticles on plant's productions for human consumptions.

Study of magnetic and electrical properties of nanocrystalline Mn doped NiO.

PubMed

Raja, S Philip; Venkateswaran, C

2011-03-01

Diluted Magnetic Semiconductors (DMS) are intensively explored in recent years for its applications in spintronics, which is expected to revolutionize the present day information technology. Nanocrystalline Mn doped NiO samples were prepared using chemical co-precipitation method with an aim to realize room temperature ferromagnetism. Phase formation of the samples was studied using X-ray diffraction-Rietveld analysis. Scanning electron microscopy and Energy dispersive X-ray analysis results reveal the nanocrystalline nature of the samples, agglomeration of the particles, considerable particle size distribution and the near stoichiometry. Thermomagnetic curves confirm the single-phase formation of the samples up to 1% doping of Mn. Vibrating Sample Magnetometer measurements indicate the absence of ferromagnetism at room temperature. This may be due to the low concentration of Mn2+ ions having weak indirect coupling with Ni2+ ions. The lack of free carriers is also expected to be the reason for the absence of ferromagnetism, which is in agreement with the results of resistivity measurements using impedance spectroscopy. Arrhenius plot shows the presence of two thermally activated regions and the activation energy for the nanocrystalline Mn doped sample was found to be greater than that of undoped NiO. This is attributed to the doping effect of Mn. However, the dielectric constant of the samples was found to be of the same order of magnitude very much comparable with that of undoped NiO.

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles

PubMed Central

Abrar, Md Abu; Dong, Yue; Lee, Paul Kyuheon; Kim, Woo Soo

2016-01-01

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration. PMID:27465437

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles

NASA Astrophysics Data System (ADS)

Abrar, Md Abu; Dong, Yue; Lee, Paul Kyuheon; Kim, Woo Soo

2016-07-01

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration.

Modeling and numerical simulations of growth and morphologies of three dimensional aggregated silver films

NASA Astrophysics Data System (ADS)

Davis, L. J.; Boggess, M.; Kodpuak, E.; Deutsch, M.

2012-11-01

We report on a model for the deposition of three dimensional, aggregated nanocrystalline silver films, and an efficient numerical simulation method developed for visualizing such structures. We compare our results to a model system comprising chemically deposited silver films with morphologies ranging from dilute, uniform distributions of nanoparticles to highly porous aggregated networks. Disordered silver films grown in solution on silica substrates are characterized using digital image analysis of high resolution scanning electron micrographs. While the latter technique provides little volume information, plane-projected (two dimensional) island structure and surface coverage may be reliably determined. Three parameters governing film growth are evaluated using these data and used as inputs for the deposition model, greatly reducing computing requirements while still providing direct access to the complete (bulk) structure of the films throughout the growth process. We also show how valuable three dimensional characteristics of the deposited materials can be extracted using the simulated structures.

Interaction of DNA bases with silver nanoparticles: assembly quantified through SPRS and SERS.

PubMed

Basu, Soumen; Jana, Subhra; Pande, Surojit; Pal, Tarasankar

2008-05-15

Colloidal silver nanoparticles were prepared by reducing silver nitrate with sodium borohydride. The synthesized silver particles show an intense surface plasmon band in the visible region. The work reported here describes the interaction between nanoscale silver particles and various DNA bases (adenine, guanine, cytosine, and thymine), which are used as molecular linkers because of their biological significance. In colloidal solutions, the color of silver nanoparticles may range from red to purple to orange to blue, depending on the degree of aggregation as well as the orientation of the individual particles within the aggregates. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and absorption spectroscopy were used to characterize the assemblies. DNA base-induced differential silver nanoparticle aggregation was quantified from the peak separation (relates to color) of surface plasmon resonance spectroscopy (SPRS) and the signal intensity of surface-enhanced Raman scattering (SERS), which rationalize the extent of silver-nucleobase interactions.

Formation of hybrid nanocomposites polymethylolacrylamide/silver

NASA Astrophysics Data System (ADS)

Kolzunova, L. G.; Shchitovskaya, E. V.; Rodzik, I. G.

2018-05-01

In this study, polymethylolacrylamide/silver composites have been formed by incorporating silver nanoparticles into the pre-electrosynthesized polymer film. The composites were formed in a two-step process involving the sorption of silver nitrate by a polymer matrix followed by chemical reduction of Ag-ions. The presence of crystalline silver phase in the polymer was confirmed by X-ray phase analysis (XRD), plasmon resonance and scanning electron microscopy (SEM). The small-angle X-ray scattering (SAXS) method has obtained the distribution functions of silver particles over radii. It is established that the content of silver in composites without chitosan is 10-15 times higher than with its additive. The dependences of cyclic voltammetry in pure phosphate buffer (pH 6.86) and in the presence of hydrogen peroxide were obtained. It has been shown that polymer/silver composites exhibit selectivity to hydrogen peroxide.

Silver ion-enhanced particle-specific cytotoxicity of silver nanoparticles and effect on the production of extracellular secretions of Phanerochaete chrysosporium.

PubMed

Huang, Zhenzhen; Xu, Piao; Chen, Guiqiu; Zeng, Guangming; Chen, Anwei; Song, Zhongxian; He, Kai; Yuan, Lei; Li, Hui; Hu, Liang

2018-04-01

This study investigated the influence of silver ions (Ag + ) on the cytotoxicity of silver nanoparticles (AgNPs) in Phanerochaete chrysosporium and noted the degree of extracellular secretions in response to the toxicant's stress. Oxalate production was elicited with moderate concentrations of 2,4-dichlorophenol (2,4-DCP) and AgNPs reaching a plateau at 10 mg/L and 10 μM, respectively. Increased oxalate accumulation was accompanied by higher activities of manganese peroxidase (MnP) and lignin peroxidase (LiP). However, the secretion of oxalate, MnP and LiP was significantly inhibited owing to Ag + incorporation into AgNP solution. Production of extracellular polymeric substances (EPS) significantly elevated with an increase in 2,4-DCP concentrations; however, after 24 h of exposure to 100 mg/L 2,4-DCP, an obvious decrease in EPS occurred, indicating that part of EPS could be consumed as carbon and energy sources to ameliorate biological tolerance to toxic stress. Furthermore, AgNP-induced "particle-specific" cytotoxicity was substantially enhanced with additional Ag + as evidenced by its significant negative impact on cellular growth, plasma membrane integrity, and morphological preservation compared with AgNPs at equal Ag concentration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Rapid Fabrication of Silver Nanowires through Photoreduction of Silver Nitrate from an Anodic-Aluminum-Oxide Template

NASA Astrophysics Data System (ADS)

Lin, Yu-Hsuan; Chen, Kun-Tso; Ho, Jeng-Rong

2011-06-01

A method for rapidly fabricating dense and high-aspect-ratio silver nanowires, with wire diameter of 200 nm and wire length more than 30 µm, is reported. The fabrication process simply involves filling the silver nitrate solution into the pores of an anodic-aluminum-oxide (AAO) membrane through capillary attraction and irradiating the dried template AAO membrane using a pulsed ArF excimer laser. Through varying the thickness and pore diameter of the employed AAO membrane, the primary dimensions of the targeted silver nanowires can be plainly specified; and, by amending the initial concentration of the silver nitrate solution and adjusting the laser operation parameters, laser fluence and number of laser pulses, the surface morphology and size of the resulting nanowires can be finely regulated. The wire formation mechanism is considered through two stages: the period of precipitation of silver particles from the dried silver nitrate film through the laser-induced photoreduction; and, the phase of clustering, merging and fusing of the reduced particles to form nanowires in the template pores by the thermal energy owing to photothermal effect. This approach is straightforward and takes the advantage that all the fabrication processes can be executed in an ambient environment and at room temperature. In addition, by the excellence in local processing that the laser possesses, this method is suitable for precisely growing nanowires.

In vitro percutaneous penetration and characterization of silver from silver-containing textiles

PubMed Central

Bianco, Carlotta; Kezic, Sanja; Crosera, Matteo; Svetličić, Vesna; Šegota, Suzana; Maina, Giovanni; Romano, Canzio; Larese, Francesca; Adami, Gianpiero

2015-01-01

The objective of this study was to determine the in vitro percutaneous penetration of silver and characterize the silver species released from textiles in different layers of full thickness human skin. For this purpose, two different wound dressings and a garment soaked in artificial sweat were placed in the donor compartments of Franz cells for 24 hours. The concentration of silver in the donor phase and in the skin was determined by an electrothermal atomic absorption spectrometer (ET-AAS) and by inductively coupled plasma mass spectrometer (ICP-MS). The characterization of silver species in the textiles and in the skin layers was made by scanning electron microscopy with integrated energy dispersive X-ray spectroscopy (SEM-EDX). Additionally, the size distribution of silver nanoparticles in the textiles was performed by atomic force microscopy (AFM). On the surface of all investigated materials, silver nanoparticles of different size and morphology were found. Released silver concentrations in the soaking solutions (ie, exposure concentration) ranged from 0.7 to 4.7 μg/mL (0.6–4.0 μg/cm2), fitting the bactericidal range. Silver and silver chloride aggregates at sizes of up to 1 μm were identified both in the epidermis and dermis. The large size of these particles suggests that the aggregation occurred in the skin. The formation of these aggregates likely slowed down the systemic absorption of silver. Conversely, these aggregates may form a reservoir enabling prolonged release of silver ions, which might lead to local effects. PMID:25792824

Pseudomonas deceptionensis DC5-mediated synthesis of extracellular silver nanoparticles.

PubMed

Jo, Jae H; Singh, Priyanka; Kim, Yeon J; Wang, Chao; Mathiyalagan, Ramya; Jin, Chi-Gyu; Yang, Deok C

2016-09-01

The biological synthesis of metal nanoparticles is of great interest in the field of nanotechnology. The present work highlights the extracellular biological synthesis of silver nanoparticles using Pseudomonas deceptionensis DC5. The particles were synthesized in the culture supernatant within 48 h of incubation. Extracellular synthesis of silver nanoparticles in the culture supernatant was confirmed by ultraviolet-visible spectroscopy, which showed the absorption peak at 428 nm, and also under field emission transmission electron microscopy which displayed the spherical shape. In addition, the particles were characterized by X-ray diffraction spectroscopy, which corresponds to the crystalline nature of nanoparticles, and energy-dispersive X-ray analysis which exhibited the intense peak at 3 keV, resembling the silver nanoparticles. Further, the synthesized nanoparticles were examined by elemental mapping which displayed the dominance of the silver element in the synthesized product, and dynamic light scattering which showed the distribution of silver nanoparticles with respect to intensity, volume, and number of particles. Moreover, the silver nanoparticles have been found to be quite active in antimicrobial activity and biofilm inhibition activity against pathogenic microorganisms. Thus, the present work emphasized the prospect of using the P. deceptionensis DC5 to achieve the extracellular synthesis of silver nanoparticles in a facile and environmental manner.

Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, X. D., E-mail: renxd@mail.ujs.edu.cn; Liu, R.; Zheng, L. M.

2015-10-05

To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphousmore » carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.« less

Antibacterial and catalytic activities of green synthesized silver nanoparticles.

PubMed

Bindhu, M R; Umadevi, M

2015-01-25

The aqueous beetroot extract was used as reducing agent for silver nanoparticles synthesis. The synthesized nanoparticles were characterized using UV-visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface plasmon resonance peak of synthesized nanoparticles was observed at 438 nm. As the concentration of beetroot extract increases, absorption spectra shows blue shift with decreasing particle size. The prepared silver nanoparticles were well dispersed, spherical in shape with the average particle size of 15 nm. The prepared silver nanoparticles are effective in inhibiting the growth of both gram positive and gram negative bacteria. The prepared silver nanoparticles reveal faster catalytic activity. This natural method for synthesis of silver nanoparticles offers a valuable contribution in the area of green synthesis and nanotechnology avoiding the presence of hazardous and toxic solvents and waste. Copyright © 2014 Elsevier B.V. All rights reserved.

Physical Characterization of Orthorhombic AgInS2 Nanocrystalline Thin Films

NASA Astrophysics Data System (ADS)

El Zawawi, I. K.; Mahdy, Manal A.

2017-11-01

Nanocrystalline thin films of AgInS2 were synthesized using an inert gas condensation technique. The grazing incident in-plane x-ray diffraction technique was used to detect the crystal structure of the deposited and annealed thin films. The results confirmed that the as-deposited film shows an amorphous behavior and that the annealed film has a single phase crystallized in an orthorhombic structure. The orthorhombic structure and particle size were detected using high-resolution transmission electron microscopy. The particle size ( P_{{s}}) estimated from micrograph images of the nanocrystalline films were increased from 6 nm to 12 nm as the film thickness increased from 11 nm to 110 nm. Accordingly, increasing the film thickness up to 110 nm reflects varying the optical band gap from 2.75 eV to 2.1 eV. The photocurrent measurements were studied where the fast rise and decay of the photocurrent are governed by the recombination mechanism. The electrical conductivity behavior was demonstrated by two transition mechanisms: extrinsic transition for a low-temperature range (300-400 K) and intrinsic transition for the high-temperature region above 400 K.

Highly surface-roughened quasi-spherical silver powders in back electrode paste for silicon solar cells

NASA Astrophysics Data System (ADS)

Yin, Peng; Liu, Shouchao; Li, Qiuying; Chen, Xiaolei; Guo, Weihong; Wu, Chifei

2017-08-01

In our work, highly surface-roughened quasi-spherical silver powders with controllable size and superior dispersibility, which have narrow size distribution and relatively high tap density, were successfully prepared by reducing silver nitrate with ascorbic acid in aqueous solutions. Gum arabic (AG) was selected as dispersant to prevent the agglomeration of silver particles. Furthermore, the effects of preparation conditions on the characteristics of the powders were systematically investigated. By varying the concentration of the reactants, dosage of dispersant, the feeding modes, synthesis temperature and the pH value of the mixture solution of silver nitrate and AG, the resulted silver particles displayed controllable size, different morphologies and surface roughness. The spherical silver powder with mean particle size of 1.20 µm, tap density of 4.1 g cm-3 and specific area value of 0.46 m2 g-1 was prepared by adjusting preparation conditions. The AG absorbed on the surface preventing the silver particles from diffusion and aggregation was proved by the ultraviolet spectra. Observations of SEM images showed that the as-prepared silver powders were relatively monodisperse silver spheres with highly roughened surface and the particle size was controllable from 1 µm to 5 µm, specific surface area value from approximately 0.2 m2 g-1 to 0.8 m2 g-1. X-ray diffraction (XRD) patterns, energy dispersive spectroscopy (EDS), x-ray photoelectron spectra (XPS) and thermal gravity analysis (TGA) demonstrated high crystallinity and purity of the obtained silver powders.

Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

NASA Astrophysics Data System (ADS)

Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

2012-10-01

Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings.

PubMed

Wang, Yuxin; Cheng, Guang; Tay, See Leng; Guo, Yunxia; Sun, Xin; Gao, Wei

2017-08-10

In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.

Influence of Weak External Magnetic Field on Amorphous and Nanocrystalline Fe-based Alloys

NASA Astrophysics Data System (ADS)

Degmová, J.; Sitek, J.

2010-07-01

Nanoperm, Hitperm and Finamet amorphous and nanocrystalline alloys were measured by Mössbauer spectrometry in a weak external magnetic field of 0.5 T. It was shown that the most sensitive parameters of Mössbauer spectra are the intensities of the 2nd and the 5th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline Nanoperm showed the increase in A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous subspectrum under the influence of magnetic field. Spectrum of nanocrystalline Finemet shown decrease in A23 parameter from 3.5 to 2.6 almost without a change in the internal magnetic field value. In the case of amorphous Nanoperm and Finemet samples, the changes are almost negligible. Hitperm alloy showed the highest sensitivity to the weak magnetic field, when the A23 parameter increased from 0.4 to 2.5 in the external magnetic fields. The A23 parameter of crystalline subspectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous subspectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within the three-level relaxation model of magnetic dynamics in an assembly of single-domain particles.

The electrodeposition of silver composites using deep eutectic solvents.

PubMed

Abbott, Andrew P; El Ttaib, Khalid; Frisch, Gero; Ryder, Karl S; Weston, David

2012-02-21

Silver is an important metal for electronic connectors, however, it is extremely soft and wear can be a significant issue. This paper describes how improved wear resistant silver coatings can be obtained from the electrolytic deposition of silver from a solution of AgCl in an ethylene glycol/choline chloride based Deep Eutectic Solvent. An up to 10-fold decrease in the wear volume is observed by the incorporation of SiC or Al(2)O(3) particles. The work also addresses the fundamental aspect of speciation of silver chloride in solution using EXAFS to probe solution structure. The size but not the nature of the composite particles is seen to change the morphology and grain size of the silver deposit. Grain sizes are shown to be consistent with previous nucleation studies. The addition of LiF is found to significantly affect the deposit morphology and improve wear resistance.

Nanocrystalline zirconia can be amorphized by ion irradiation.

PubMed

Meldrum, A; Boatner, L A; Ewing, R C

2002-01-14

Nanocrystalline composites are finding applications in high-radiation environments due to their excellent mechanical and electronic properties. We show, however, that at the smallest particle sizes, radiation damage effects can be so strongly enhanced that under the right conditions, materials that have never been made amorphous can become highly susceptible to irradiation-induced amorphization. Because light-weight, high-strength nanocomposites are potential materials for spacecraft shielding and sensor systems, these fundamental results have significant implications for the design and selection of materials to be used in environments where a large ion flux will be encountered.

Synthesis and optical properties of silver nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Jaiveer; Kaurav, Netram, E-mail: netramkaurav@yahoo.co.uk; Choudhary, K. K.

The preparation of stable, uniform silver nanoparticles by reduction of silver acetate by ethylene glycol (EG) is reported in the present paper. It is a simple process of recent interest for obtaining silver nanoparticles. The samples were characterized by X-Ray diffraction (XRD), which reveals an average particle size (D) of 38 nm. The UV/Vis spectra show that an absorption peak, occurring due to surface plasmon resonance (SPR), exists at 319 nm.

Maple leaf (Acer sp.) extract mediated green process for the functionalization of ZnO powders with silver nanoparticles.

PubMed

Vivekanandhan, Singaravelu; Schreiber, Makoto; Mason, Cynthia; Mohanty, Amar Kumar; Misra, Manjusri

2014-01-01

The functionalization of ZnO powders with silver nanoparticles (AgNPs) through a novel maple leaf extract mediated biological process was demonstrated. Maple leaf extract was found to be a very effective bioreduction agent for the reduction of silver ions. The reduction rate of Ag(+) into Ag(0) was found to be much faster than other previously reported bioreduction rates and was comparable to the reduction rates obtained through chemical means. The functionalization of ZnO particles with silver nanoparticles through maple leaf extract mediated bioreduction of silver was investigated through UV-visible spectrophotometry, transmission electron microscopy (TEM), and X-ray diffraction analysis. It was found that the ZnO particles were coated with silver nanoparticles 5-20 nm in diameter. The photocatalytic ability of the ZnO particles functionalized with silver nanoparticles was found to be significantly improved compared to the photocatalytic ability of the neat ZnO particles. The silver functionalized ZnO particles reached 90% degradation of the dye an hour before the neat ZnO particles. Copyright © 2013 Elsevier B.V. All rights reserved.

Detection of colloidal silver chloride near solubility limit

NASA Astrophysics Data System (ADS)

Putri, K. Y.; Adawiah, R.

2018-03-01

Detection of nanoparticles in solution has been made possible by several means; one of them is laser-induced breakdown detection (LIBD). LIBD is able to distinguish colloids of various sizes and concentrations. This technique has been used in several solubility studies. In this study, the formation of colloids in a mixed system of silver nitrate and sodium chloride was observed by acoustic LIBD. Silver chloride has low solubility limit, therefore LIBD measurement is appropriate. Silver and chloride solutions with equal concentrations, set at below and above the solubility of silver chloride as the expected solid product, were mixed and the resulting colloids were observed. The result of LIBD measurement showed that larger particles were present as more silver and chloride introduced. However, once the concentrations exceeded the solubility limit of silver chloride, the detected particle size seemed to be decreasing, hence suggested the occurrence of coprecipitation process. This phenomenon indicated that the ability of LIBD to detect even small changes in colloid amounts might be a useful tool in study on formation and stability of colloids, i.e. to confirm whether nanoparticles synthesis has been successfully performed and whether the system is stable or not.

Silver distribution and release from an antimicrobial denture base resin containing silver colloidal nanoparticles.

PubMed

Monteiro, Douglas Roberto; Gorup, Luiz Fernando; Takamiya, Aline Satie; de Camargo, Emerson Rodrigues; Filho, Adhemar Colla Ruvolo; Barbosa, Debora Barros

2012-01-01

The aim of this study was to evaluate a denture base resin containing silver colloidal nanoparticles through morphological analysis to check the distribution and dispersion of these particles in the polymer and by testing the silver release in deionized water at different time periods. A Lucitone 550 denture resin was used, and silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The acrylic resin was prepared in accordance with the manufacturers' instructions, and silver nanoparticle suspension was added to the acrylic resin monomer in different concentrations (0.05, 0.5, and 5 vol% silver colloidal). Controls devoid of silver nanoparticles were included. The specimens were stored in deionized water at 37°C for 7, 15, 30, 60, and 120 days, and each solution was analyzed using atomic absorption spectroscopy. Silver was not detected in deionized water regardless of the silver nanoparticles added to the resin and of the storage period. Micrographs showed that with lower concentrations, the distribution of silver nanoparticles was reduced, whereas their dispersion was improved in the polymer. Moreover, after 120 days of storage, nanoparticles were mainly located on the surface of the nanocomposite specimens. Incorporation of silver nanoparticles in the acrylic resin was evidenced. Moreover, silver was not detected by the detection limit of the atomic absorption spectrophotometer used in this study, even after 120 days of storage in deionized water. Silver nanoparticles are incorporated in the PMMA denture resin to attain an effective antimicrobial material to help control common infections involving oral mucosal tissues in complete denture wearers. © 2011 by the American College of Prosthodontists.

Procedure optimization for green synthesis of silver nanoparticles by aqueous extract of Eucalyptus oleosa.

PubMed

Pourmortazavi, Seied Mahdi; Taghdiri, Mehdi; Makari, Vajihe; Rahimi-Nasrabadi, Mehdi

2015-02-05

The present study is dealing with the green synthesis of silver nanoparticles using the aqueous extract of Eucalyptus oleosa as a green synthesis procedure without any catalyst, template or surfactant. Colloidal silver nanoparticles were synthesized by reacting aqueous AgNO3 with E. oleosa leaf extract at non-photomediated conditions. The significance of some synthesis conditions such as: silver nitrate concentration, concentration of the plant extract, time of synthesis reaction and temperature of plant extraction procedure on the particle size of synthesized silver particles was investigated and optimized. The participations of the studied factors in controlling the particle size of reduced silver were quantitatively evaluated via analysis of variance (ANOVA). The results of this investigation showed that silver nanoparticles could be synthesized by tuning significant parameters, while performing the synthesis procedure at optimum conditions leads to form silver nanoparticles with 21nm as averaged size. Ultraviolet-visible spectroscopy was used to monitor the development of silver nanoparticles formation. Meanwhile, produced silver nanoparticles were characterized by scanning electron microscopy, energy-dispersive X-ray, and FT-IR techniques. Copyright © 2014 Elsevier B.V. All rights reserved.

Laser synthesis and spectroscopy of acetonitrile/silver nanoparticles

NASA Astrophysics Data System (ADS)

Akin, S. T.; Liu, X.; Duncan, M. A.

2015-11-01

Silver nanoparticles with acetonitrile ligands are produced in a laser ablation flow reactor. Excimer laser ablation produces gas phase metal clusters which are thermalized with helium or argon collisions in the flowtube, and reactions with acetonitrile vapor coordinate this ligand to the particle surface. The gaseous mixture is captured in a cryogenic trap; warming produces a solution of excess ligand and coated particles. TEM images reveal particle sizes of 10-30 nm diameter. UV-vis absorption and fluorescence spectra are compared to those of standard silver nanoparticles with surfactant coatings. Deep-UV ligand absorption is strongly enhanced by nanoparticle adsorption.

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core.

PubMed

Richter, Alexander P; Brown, Joseph S; Bharti, Bhuvnesh; Wang, Amy; Gangwal, Sumit; Houck, Keith; Cohen Hubal, Elaine A; Paunov, Vesselin N; Stoyanov, Simeon D; Velev, Orlin D

2015-09-01

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

Solid state consolidation nanocrystalline copper-tungsten using cold spray

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Aaron Christopher; Sarobol, Pylin; Argibay, Nicolas

It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. Wemore » demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.« less

Evaluation on the Presence of Nano Silver Particle in Improving a Conventional Water-based Drilling Fluid

NASA Astrophysics Data System (ADS)

Husin, H.; Ahmad, N.; Jamil, N.; Chyuan, O. H.; Roslan, A.

2018-05-01

Worldwide demand in oil and gas energy consumption has been driving many of oil and gas companies to explore new oil and gas resource field in an ultra-deep water environment. As deeper well is drilled, more problems and challenges are expected. The successful of drilling operation is highly dependent on properties of drilling fluids. As a way to operate drilling in challenging and extreme surroundings, nanotechnology with their unique properties is employed. Due to unique physicochemical, electrical, thermal, hydrodynamic properties and exceptional interaction potential of nanomaterials, nanoparticles are considered to be the most promising material of choice for smart fluid design for oil and gas field application. Throughout this paper, the effect of nano silver particle in improving a conventional water based drilling fluid was evaluated. Results showed that nano silver gave a significant improvement to the conventional water based drilling fluid in terms of its rheological properties and filtration test performance.

A novel cetyltrimethyl ammonium silver bromide complex and silver bromide nanoparticles obtained by the surfactant counterion.

PubMed

Liu, Xian-Hao; Luo, Xiao-Hong; Lu, Shu-Xia; Zhang, Jing-Chang; Cao, Wei-Liang

2007-03-01

A novel cetyltrimethyl ammonium silver bromide (CTASB) complex has been prepared simply through the reaction of silver nitrate with cetyltrimethyl ammonium bromide (CTAB) in aqueous solution at room temperature by controlling the concentration of CTAB and the molar ratio of CTAB to silver nitrate in the reaction solution, in which halogen in CTAB is used as surfactant counterion. The structure and thermal behavior of cetyltrimethyl ammonium silver bromide have been investigated by using X-ray diffraction (XRD), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), UV/vis spectroscopy, thermal analysis (TG-DTA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that the complex possesses a metastable layered structure. Upon heating the CTASB aqueous dispersion to above 80 degrees C, the structure change of the complex took place and CTAB-capped nanosized silver bromide particles further formed.

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuxin; Cheng, Guang; Tay, See Leng

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

DOE PAGES

Wang, Yuxin; Cheng, Guang; Tay, See Leng; ...

2017-08-10

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

Micromechanics Modeling of Fracture in Nanocrystalline Metals

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Piascik, R. S.; Raju, I. S.; Harris, C. E.

2002-01-01

Nanocrystalline metals have very high theoretical strength, but suffer from a lack of ductility and toughness. Therefore, it is critical to understand the mechanisms of deformation and fracture of these materials before their full potential can be achieved. Because classical fracture mechanics is based on the comparison of computed fracture parameters, such as stress intlmsity factors, to their empirically determined critical values, it does not adequately describe the fundamental physics of fracture required to predict the behavior of nanocrystalline metals. Thus, micromechanics-based techniques must be considered to quanti@ the physical processes of deformation and fracture within nanocrystalline metals. This paper discusses hndamental physicsbased modeling strategies that may be useful for the prediction Iof deformation, crack formation and crack growth within nanocrystalline metals.

THERMALLY STABLE NANOCRYSTALLINE TIO2 PHOTOCATALYSTS SYNTHESIZED VIA SOL-GEL METHODS MODIFIED WITH IONIC LIQUID AND SURFACTANT MOLECULES

EPA Science Inventory

Recently, sol-gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO₂ particles via an alkoxide sol-gel method employing a water-immi...

Direct patterning of silver particles on porous silicon by inkjet printing of a silver salt via in-situ reduction

PubMed Central

2012-01-01

We have developed a method for obtaining a direct pattern of silver nanoparticles (NPs) on porous silicon (p-Si) by means of inkjet printing (IjP) of a silver salt. Silver NPs were obtained by p-Si mediated in-situ reduction of Ag+ cations using solutions based on AgNO3 which were directly printed on p-Si according to specific geometries and process parameters. The main difference with respect to existing literature is that normally, inkjet printing is applied to silver (metal) NP suspensions, while in our experiment the NPs are formed after jetting the solution on the reactive substrate. We performed both optical and scanning electron microscopes on the NPs traces, correlating the morphology features with the IjP parameters, giving an insight on the synthesis kinetics. The patterned NPs show good performances as SERS substrates. PMID:22953722

Enhancement of Single Molecule Fluorescence Signals by Colloidal Silver Nanoparticles in Studies of Protein Translation

PubMed Central

Bharill, Shashank; Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Mandecki, Wlodek; Gryczynski, Ignacy; Gryczynski, Zygmunt; Cooperman, Barry S.; Goldman, Yale E.

2011-01-01

Metal enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold respectively. Fluorescence intensity fluctuations above shot noise, at 0.1 – 5 Hz, were greater on silver particles. Overall signal to noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G. PMID:21158483

Enhancement of single-molecule fluorescence signals by colloidal silver nanoparticles in studies of protein translation.

PubMed

Bharill, Shashank; Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Mandecki, Wlodek; Gryczynski, Ignacy; Gryczynski, Zygmunt; Cooperman, Barry S; Goldman, Yale E

2011-01-25

Metal-enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold, respectively. Fluorescence intensity fluctuations above shot noise, at 0.1-5 Hz, were greater on silver particles. Overall signal-to-noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G.

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} as a gas sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shinde, Tukaram J., E-mail: pshindetj@yahoo.co.in; Gadkari, Ashok B.; Jadhav, Sarjerao R.

2015-06-24

Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl{sub 2}, LPG and C{sub 2}H{sub 5}OH. It was observed that NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

Antimicrobial action of silver nitrate.

PubMed

Richards, R M

1981-01-01

Silver nitrate 3 mug/ml prevented the separation into two daughter cells of sensitive dividing cells of Pseudomonas aeruginosa growing in nutrient broth plus the chemical. Cell size of sensitive cells was increased and the cytoplasmic contents, cytoplasmic membrane and external cell envelope structures were all abnormal. P. aeruginosa cells grown in the presence of silver nitrate 9 mug/ml showed all these changes to a marked degree except inhibition of cell division was not observed. Silver nitrate (1.5 mug/ml) in distilled water inactivated bacteriophage T2 particles as determined by their infectivity to Escherichia coli B cultures. Lysozyme (50 mug/ml) reduced, and sodium chloride (0.9%) blocked this activity.

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core. Structure, dissolution in cell culture media, and biological impact on macrophages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.

Widespread use of silver nanoparticles raises questions of environmental impact and toxicity. Both silver particles and silver ions formed by particle dissolution may impact biological systems. Therefore it is important to understand the characteristics of silver nanoparticles and their stability in relevant media. The synthesis route can impact physical and chemical characteristics of the particles and we report the characterization and solution stability of three types of silver nanoparticles (20 nm particles with and without gold cores and 110 nm particles with gold cores) in cell culture media with serum proteins: FBS10%/RPMI. These nanoparticles were synthesized in aqueous solution andmore » characterized using both in situ and ex situ analysis methods. Dissolution studies were carried at particle concentrations from 1 µg/ml to 50 µg/ml. Particles with gold cores had smaller crystallite size and higher apparent solubility than pure silver particles. A dissolution model was found to describe the time variation of particle size and amount of dissolved silver for particle loadings above 9 µg/ml. An effective solubility product obtained from fitting the data was higher for the 20 nm gold core particles in comparison to the pure silver or 110 nm particles. Dissolution of the nanoparticles was enhanced by presence of serum proteins contained in fetal bovine serum. In addition, the protocol of the dispersion in the medium was found to influence particle agglomeration and dissolution. Results show that particle structure can impact the concentration of dissolved silver and the dose to which cells would be exposed during in vitro studies.« less

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core. Structure, dissolution in cell culture media, and biological impact on macrophages

DOE PAGES

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.; ...

2015-07-15

Widespread use of silver nanoparticles raises questions of environmental impact and toxicity. Both silver particles and silver ions formed by particle dissolution may impact biological systems. Therefore it is important to understand the characteristics of silver nanoparticles and their stability in relevant media. The synthesis route can impact physical and chemical characteristics of the particles and we report the characterization and solution stability of three types of silver nanoparticles (20 nm particles with and without gold cores and 110 nm particles with gold cores) in cell culture media with serum proteins: FBS10%/RPMI. These nanoparticles were synthesized in aqueous solution andmore » characterized using both in situ and ex situ analysis methods. Dissolution studies were carried at particle concentrations from 1 µg/ml to 50 µg/ml. Particles with gold cores had smaller crystallite size and higher apparent solubility than pure silver particles. A dissolution model was found to describe the time variation of particle size and amount of dissolved silver for particle loadings above 9 µg/ml. An effective solubility product obtained from fitting the data was higher for the 20 nm gold core particles in comparison to the pure silver or 110 nm particles. Dissolution of the nanoparticles was enhanced by presence of serum proteins contained in fetal bovine serum. In addition, the protocol of the dispersion in the medium was found to influence particle agglomeration and dissolution. Results show that particle structure can impact the concentration of dissolved silver and the dose to which cells would be exposed during in vitro studies.« less

Glass frits coated with silver nanoparticles for silicon solar cells

NASA Astrophysics Data System (ADS)

Li, Yingfen; Gan, Weiping; Zhou, Jian; Li, Biyuan

2015-06-01

Glass frits coated with silver nanoparticles were prepared by electroless plating. Gum Arabic (GA) was used as the activating agent of glass frits without the assistance of stannous chloride or palladium chloride. The silver-coated glass frits prepared with different GA dosages were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The characterization results indicated that silver-coated glass frits had the structures of both glass and silver. Spherical silver nanoparticles were distributed on the glass frits evenly. The density and particle size of silver nanoparticles on the glass frits can be controlled by adjusting the GA dosage. The silver-coated glass frits were applied to silver pastes to act as both the densification promoter and silver crystallite formation aid in the silver electrodes. The prepared silver-coated glass frits can improve the photovoltaic performances of solar cells.

Synthesis of Silver Polymer Nanocomposites and Their Antibacterial Activity

NASA Astrophysics Data System (ADS)

Gavade, Chaitali; Shah, Sunil; Singh, N. L.

2011-07-01

PVA (Polyvinyl Alcohol) silver nanocomposites of different sizes were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and amine hydrazine as a reducing agent. The formation of the silver nanoparticles was noticed using UV- visible absorption spectroscopy. The UV-visible spectroscopy revealed the formation of silver nanoparticles by exhibiting the surface plasmon resonance. The bactericidal activity due to silver release from the surface was determined by the modification of conventional diffusion method. Salmonella typhimurium, Serratia sps and Shigella sps were used as test bacteria which are gram-negative type bacteria. Effect of the different sizes of silver nano particles on antibacterial efficiency was discussed. Zones of inhibition were measured after 24 hours of incubation at 37 °C which gave 20 mm radius for high concentration of silver nanoparticles.

Method of making nanocrystalline alpha alumina

DOEpatents

Siegel, Richard W.; Hahn, Horst; Eastman, Jeffrey A.

1992-01-01

Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.

Electrical conductivity modification using silver nano particles of Jatropha Multifida L. and Pterocarpus Indicus w. extracts films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diantoro, Markus, E-mail: markus.diantoro.fmipa@um.ac.id; Hidayati, Nisfi Nahari Sani; Latifah, Rodatul

Natural polymers can be extracted from leaf or stem of plants. Pterocarpus Indicus W. (PIW) and Jatropha Multifida L. (JIL) plants are good candidate as natural polymer sources. PIW and JIW polymers contain chemical compound so-called flavonoids which has C{sub 6}-C{sub 3}-C{sub 6} carbons conjugated configuration. The renewable type of polymer as well as their abundancy of flavonoid provide us to explore their physical properties. A number of research have been reported related to broad synthesis method and mechanical properties. So far there is no specific report of electrical conductivity associated to PIW and JIL natural polymers. In order tomore » obtain electrical conductivity and its crystallinity of the extracted polymer films, it was induced on them a various fraction of silver nano particles. The film has been prepared by means of spin coating method on nickel substrate. It was revealed that FTIR spectra confirm the existing of rutine flavonoid. The crystallinity of the samples increase from 0.66%, to 4.11% associated to the respective various of silver fractions of 0.1 M to 0.5 M. SEM images show that there are some grains of silver in the film. The nature of electric conductivity increases a long with the addition of silver. The electrical conductivity increase significantly from 3.22 S/cm, to 542.85 S/cm. On the other hand, PIW films also shows similar trends that increase of Ag induce the increase its crystallinity as well as its electrical conductivity at semiconducting level. This result opens a prospective research and application of the green renewable polymer as optoelectronic materials.« less

Electrical conductivity modification using silver nano particles of Jatropha Multifida L. and Pterocarpus Indicus w. extracts films

NASA Astrophysics Data System (ADS)

Diantoro, Markus; Hidayati, Nisfi Nahari Sani; Latifah, Rodatul; Fuad, Abdulloh; Nasikhudin, Sujito, Hidayat, Arif

2016-03-01

Natural polymers can be extracted from leaf or stem of plants. Pterocarpus Indicus W. (PIW) and Jatropha Multifida L. (JIL) plants are good candidate as natural polymer sources. PIW and JIW polymers contain chemical compound so-called flavonoids which has C6-C3-C6 carbons conjugated configuration. The renewable type of polymer as well as their abundancy of flavonoid provide us to explore their physical properties. A number of research have been reported related to broad synthesis method and mechanical properties. So far there is no specific report of electrical conductivity associated to PIW and JIL natural polymers. In order to obtain electrical conductivity and its crystallinity of the extracted polymer films, it was induced on them a various fraction of silver nano particles. The film has been prepared by means of spin coating method on nickel substrate. It was revealed that FTIR spectra confirm the existing of rutine flavonoid. The crystallinity of the samples increase from 0.66%, to 4.11% associated to the respective various of silver fractions of 0.1 M to 0.5 M. SEM images show that there are some grains of silver in the film. The nature of electric conductivity increases a long with the addition of silver. The electrical conductivity increase significantly from 3.22 S/cm, to 542.85 S/cm. On the other hand, PIW films also shows similar trends that increase of Ag induce the increase its crystallinity as well as its electrical conductivity at semiconducting level. This result opens a prospective research and application of the green renewable polymer as optoelectronic materials.

Alternating current transport and dielectric relaxation of nanocrystalline graphene oxide

NASA Astrophysics Data System (ADS)

Zedan, I. T.; El-Menyawy, E. M.

2018-07-01

Graphene oxide (GO) has been synthesized from natural graphite using modified Hummer's method and is subjected to sonication for 1 h. X-ray diffraction (XRD) showed that the prepared GO has nanocrystalline structure with particle size of about 5 nm and high-resolution transmission electron microscope showed that it had a layered structure. The nanocrystalline GO powder was pressed as a disk and the alternating current (AC) electrical conductivity, σAC, and dielectric properties have been investigated in the frequency range 50Hz-5 MHz and temperature range 298-523K using parallel plate spectroscopic technique. Analysis of σ AC as a function of frequency shows that the relation follows Jonscher's universal law with frequency exponent decreases with increasing temperature in which the correlated barrier hopping model is applicable to describe the behavior. The dielectric constant and dielectric loss are studied as functions of frequency and temperature. The dielectric modulus formalism is used for describing the relaxation process in which the relaxation time and its activation energy were evaluated.

In Vivo Human Time-Exposure Study of Orally Dosed Commercial Silver Nanoparticles

PubMed Central

Munger, Mark A.; Radwanski, Przemyslaw; Hadlock, Greg C.; Stoddard, Greg; Shaaban, Akram; Falconer, Jonathan; Grainger, David W.; Deering-Rice, Cassandra E.

2013-01-01

Background Human biodistribution, bioprocessing and possible toxicity of nanoscale silver receives increasing health assessment. Methods We prospectively studied commercial 10- and 32-ppm nanoscale silver particle solutions in a single-blind, controlled, cross-over, intent-to-treat, design. Healthy subjects (n=60) underwent metabolic, blood counts, urinalysis, sputum induction, and chest and abdomen magnetic resonance imaging. Silver serum and urine content was determined. Results No clinically important changes in metabolic, hematologic, or urinalysis measures were identified. No morphological changes were detected in the lungs, heart or abdominal organs. No significant changes were noted in pulmonary reactive oxygen species or pro-inflammatory cytokine generation. Conclusion In vivo oral exposure to these commercial nanoscale silver particle solutions does not prompt clinically important changes in human metabolic, hematologic, urine, physical findings or imaging morphology. Further study of increasing time exposure and dosing of silver nanoparticulate silver, and observation of additional organ systems is warranted to assert human toxicity thresholds. PMID:23811290

The dual role of silver during silicon etching in HF solution.

PubMed

Abouda-Lachiheb, Manel; Nafie, Nesma; Bouaicha, Mongi

2012-08-13

It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope.

The dual role of silver during silicon etching in HF solution

PubMed Central

2012-01-01

It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope. PMID:22888998

Biogenic synthesis of silver nanoparticles by leaf extract of Cassia angustifolia

NASA Astrophysics Data System (ADS)

Amaladhas, T. Peter; Sivagami, S.; Akkini Devi, T.; Ananthi, N.; Priya Velammal, S.

2012-12-01

In this study Cassia angustifolia (senna) is used for the environmentally friendly synthesis of silver nanoparticles. Stable silver nanoparticles having symmetric surface plasmon resonance (SPR) band centred at 420 nm were obtained within 10 min at room temperature by treating aqueous solutions of silver nitrate with C. angustifolia leaf extract. The water soluble components from the leaves, probably the sennosides, served as both reducing and capping agents in the synthesis of silver nanoparticles. The nanoparticles were characterized using UV-Vis, Fourier transform infrared (FTIR) spectroscopic techniques and transmission electron microscopy (TEM). The nanoparticles were poly-dispersed, spherical in shape with particle size in the range 9-31 nm, the average size was found to be 21.6 nm at pH 11. The zeta potential was -36.4 mV and the particles were stable for 6 months. The crystalline phase of the nanoparticles was confirmed from the selected area diffraction pattern (SAED). The rate of formation and size of silver nanoparticles were pH dependent. Functional groups responsible for capping of silver nanoparticles were identified from the FTIR spectrum. The synthesized silver nanoparticles exhibited good antibacterial potential against Escherichia coli and Staphylococcus aureus.

TEM and SP-ICP-MS analysis of the release of silver nanoparticles from decoration of pastry.

PubMed

Verleysen, E; Van Doren, E; Waegeneers, N; De Temmerman, P-J; Abi Daoud Francisco, M; Mast, J

2015-04-08

Metallic silver is an EU approved food additive referred to as E174. It is generally assumed that silver is only present in bulk form in the food chain. This work demonstrates that a simple treatment with water of "silver pearls", meant for decoration of pastry, results in the release of a subfraction of silver nanoparticles. The number-based size and shape distributions of the single, aggregated, and/or agglomerated particles released from the silver pearls were determined by combining conventional bright-field TEM imaging with semiautomatic particle detection and analysis. In addition, the crystal structure of the particles was studied by electron diffraction and chemical information was obtained by combining HAADF-STEM imaging with EDX spectroscopy and mapping. The TEM results were confirmed by SP-ICP-MS. The representative Ag test nanomaterial NM-300 K was used as a positive control to determine the uncertainty on the measurement of the size and shape of the particles.

Oxidative dissolution of silver nanoparticles: A new theoretical approach.

PubMed

Adamczyk, Zbigniew; Oćwieja, Magdalena; Mrowiec, Halina; Walas, Stanisław; Lupa, Dawid

2016-05-01

A general model of an oxidative dissolution of silver particle suspensions was developed that rigorously considers the bulk and surface solute transport. A two-step surface reaction scheme was proposed that comprises the formation of the silver oxide phase by direct oxidation and the acidic dissolution of this phase leading to silver ion release. By considering this, a complete set of equations is formulated describing oxygen and silver ion transport to and from particles' surfaces. These equations are solved in some limiting cases of nanoparticle dissolution in dilute suspensions. The obtained kinetic equations were used for the interpretation of experimental data pertinent to the dissolution kinetics of citrate-stabilized silver nanoparticles. In these kinetic measurements the role of pH and bulk suspension concentration was quantitatively evaluated by using the atomic absorption spectrometry (AAS). It was shown that the theoretical model adequately reflects the main features of the experimental results, especially the significant increase in the dissolution rate for lower pH. Also the presence of two kinetic regimes was quantitatively explained in terms of the decrease in the coverage of the fast dissolving oxide layer. The overall silver dissolution rate constants characterizing these two regimes were determined. Copyright © 2015 Elsevier Inc. All rights reserved.

Combined biocidal action of silver nanoparticles and ions against Chlorococcales (Scenedesmus quadricauda, Chlorella vulgaris) and filamentous algae (Klebsormidium sp.).

PubMed

Zouzelka, Radek; Cihakova, Pavlina; Rihova Ambrozova, Jana; Rathousky, Jiri

2016-05-01

Despite the extensive research, the mechanism of the antimicrobial and biocidal performance of silver nanoparticles has not been unequivocally elucidated yet. Our study was aimed at the investigation of the ability of silver nanoparticles to suppress the growth of three types of algae colonizing the wetted surfaces or submerged objects and the mechanism of their action. Silver nanoparticles exhibited a substantial toxicity towards Chlorococcales Scenedesmus quadricauda, Chlorella vulgaris, and filamentous algae Klebsormidium sp., which correlated with their particle size. The particles had very good stability against agglomeration even in the presence of multivalent cations. The concentration of silver ions in equilibrium with nanoparticles markedly depended on the particle size, achieving about 6 % and as low as about 0.1 % or even less for the particles 5 nm in size and for larger ones (40-70 nm), respectively. Even very limited proportion of small particles together with larger ones could substantially increase concentration of Ag ions in solution. The highest toxicity was found for the 5-nm-sized particles, being the smallest ones in this study. Their toxicity was even higher than that of silver ions at the same silver concentration. When compared as a function of the Ag(+) concentration in equilibrium with 5-nm particles, the toxicity of ions was at least 17 times higher than that obtained by dissolving silver nitrite (if not taking into account the effect of nanoparticles themselves). The mechanism of the toxicity of silver nanoparticles was found complex with an important role played by the adsorption of silver nanoparticles and the ions released from the particles on the cell surface. This mechanism could be described as some sort of synergy between nanoparticles and ions. While our study clearly showed the presence of this synergy, its detailed explanation is experimentally highly demanding, requiring a close cooperation between materials scientists

Application of thermospray flame furnace atomic absorption spectrometry for investigation of silver nanoparticles.

PubMed

Sirirat, Natnicha; Tetbuntad, Kornrawee; Siripinyanond, Atitaya

2017-03-01

Thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was applied to investigate the time-dependent absorption peak profile of various forms of silver. The thermospray flame furnace was set up with a 10-cm-long nickel tube with six holes, each 2.0 mm in diameter, to allow the flame to enter, and this nickel tube acted as a furnace. A sample of 300 μL was introduced into this furnace by use of water as a carrier at a flow rate of 0.5 mL min -1 through the ceramic capillary (0.5-mm inner diameter and 2.0-mm outer diameter), which was inserted into the front hole of the nickel tube. The system was applied to examine atomization behaviors of silver nanoparticles (AgNPs) with particle sizes ranging from 10 to 100 nm. The atomization rate of AgNPs was faster than that of the dissolved silver ion. With increased amount of silver, the decay time observed from the time-dependent absorption peak profile was shortened in the case of dissolved silver ion, but it was increased in the case of AgNPs. With the particle size ranging from 10 to 100 nm, the detection sensitivity was indirectly proportional to the particle size, suggesting that TS-FF-AAS may offer insights into the particle size of AgNPs provided that the concentration of the silver is known. To obtain quantitative information on AgNPs, acid dissolution of the particles was performed before TS-FF-AAS analysis, and recoveries of 80-110% were obtained.

Complex conductivity response to silver nanoparticles in ...

EPA Pesticide Factsheets

The increase in the use of nanoscale materials in consumer products has resulted in a growing concern of their potential hazard to ecosystems and public health from their accidental or intentional introduction to the environment. Key environmental, health, and safety research needs include knowledge and methods for their detection, characterization, fate, and transport. Specifically, techniques available for the direct detection and quantification of their fate and transport in the environment are limited. Their small size, high surface area to volume ratio, interfacial, and electrical properties make metallic nanoparticles, such as silver nanoparticles, good targets for detection using electrical geophysical techniques. Here we measured the complex conductivity response to silver nanoparticles in sand columns under varying moisture conditions (0–30%), nanoparticle concentrations (0–10 mg/g), lithology (presence of clay), pore water salinity (0.0275 and 0.1000 S/m), and particle size (35, 90–210 and 1500–2500 nm). Based on the Cole-Cole relaxation models we obtained the chargeability and the time constant. We demonstrate that complex conductivity can detect silver nanoparticles in porous media with the response enhanced by higher concentrations of silver nanoparticles, moisture content, ionic strength, clay content and particle diameter. Quantification of the volumetric silver nanoparticles content in the porous media can also be obtained from complex co

Ergonomic Synthesis Suitable for Industrial Production of Silver-Festooned Zinc Oxide Nanorods

NASA Astrophysics Data System (ADS)

Khan, G. R.; Khan, R. A.

2015-07-01

For maximizing productivity, minimizing cost, time-boxing process and optimizing human effort, a single-step, cost-effective, ultra-fast and environmentally benign synthesis suitable for industrial production of nanocrystalline ZnO, and Ag-doped ZnO has been reported in this paper. The synthesis based on microwave-supported aqueous solution method used zinc acetate dehydrate and silver nitrate as precursors for fabrication of nanorods. The synthesized products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and UV-Vis-NIR spectroscopy. The undoped and Ag-doped ZnO nanorods crystallized in a hexagonal wurtzite structure having spindle-like morphology. The blue shift occurred at absorption edge of Ag-doped ZnO around 260 nm compared to 365 nm of bulk ZnO. The red shift occurred at Raman peak site of 434 cm-1 compared to characteristic wurtzite phase peak of ZnO (437 cm-1). The bandgap energies were found to be 3.10 eV, 3.11 eV and 3.18 eV for undoped, 1% Ag-doped, and 3% Ag-doped ZnO samples, respectively. The TEM results provided average particle sizes of 17 nm, 15 nm and 13 nm for undoped, and 1% and 3% Ag-doped ZnO samples, respectively.

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages

PubMed Central

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.; Baer, Donald R.; Smith, Jordan N.; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D.; Chen, Shu; Porter, Alexandra E.; Ryan, Mary P.

2015-01-01

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies. PMID:26178265

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages.

PubMed

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H; Baer, Donald R; Smith, Jordan N; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D; Chen, Shu; Porter, Alexandra E; Ryan, Mary P

2015-09-15

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies.

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

NASA Astrophysics Data System (ADS)

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

2011-04-01

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.

The Bulk Nanocrystalline zn Produced by Mechanical Attrition

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

Preparation, characterization, and optical properties of gold, silver, and gold-silver alloy nanoshells having silica cores.

PubMed

Kim, Jun-Hyun; Bryan, William W; Lee, T Randall

2008-10-07

This report describes the structural and optical properties of a series of spherical shell/core nanoparticles in which the shell is comprised of a thin layer of gold, silver, or gold-silver alloy, and the core is comprised of a monodispersed silica nanoparticle. The silica core particles were prepared using the Stöber method, functionalized with terminal amine groups, and then seeded with small gold nanoparticles (approximately 2 nm in diameter). The gold-seeded silica particles were coated with a layer of gold, silver, or gold-silver alloy via solution-phase reduction of an appropriate metal ion or mixture of metal ions. The size, morphology, and elemental composition of the composite nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The optical properties of the nanoparticles were analyzed by UV-vis spectroscopy, which showed strong absorptions ranging from 400 nm into the near-IR region, where the position of the plasmon band reflected not only the thickness of the metal shell, but also the nature of the metal comprising the shell. Importantly, the results demonstrate a new strategy for tuning the position of the plasmon resonance without having to vary the core diameter or the shell thickness.

Timescale of silver nanoparticle transformation in neural cell cultures impacts measured cell response

NASA Astrophysics Data System (ADS)

Hume, Stephanie L.; Chiaramonti, Ann N.; Rice, Katherine P.; Schwindt, Rani K.; MacCuspie, Robert I.; Jeerage, Kavita M.

2015-07-01

Both serum protein concentration and ionic strength are important factors in nanoparticle transformation within cell culture environments. However, silver nanoparticles are not routinely tracked at their working concentration in the specific medium used for in vitro toxicology studies. Here we evaluated the transformation of electrostatically stabilized citrate nanoparticles (C-AgNPs) and sterically stabilized polyvinylpyrrolidone nanoparticles (PVP-AgNPs) in a low-serum ( 0.2 mg/mL bovine serum albumin) culture medium, while measuring the response of rat cortex neural progenitor cells, which differentiate in this culture environment. After 24 h, silver nanoparticles at concentrations up to 10 µg/mL did not affect adenosine triphosphate levels, whereas silver ions decreased adenosine triphosphate levels at concentrations of 1.1 µg/mL or higher. After 240 h, both silver nanoparticles, as well as silver ion, unambiguously decreased adenosine triphosphate levels at concentrations of 1 and 1.1 µg/mL, respectively, suggesting particle dissolution. Particle transformation was investigated in 1:10 diluted, 1:2 diluted, or undiluted differentiation medium, all having an identical protein concentration, to separate the effect of serum protein stabilization from ionic strength destabilization. Transmission electron microscopy images indicated that particles in 1:10 medium were not surrounded by proteins, whereas particles became clustered within a non-crystalline protein matrix after 24 h in 1:2 medium and at 0 h in undiluted medium. Despite evidence for a protein corona, particles were rapidly destabilized by high ionic strength media. Polyvinylpyrrolidone increased the stability of singly dispersed particles compared to citrate ligands; however, differences were negligible after 4 h in 1:2 medium or after 1 h in undiluted medium. Thus low-serum culture environments do not provide sufficient colloidal stability for long-term toxicology studies with citrate- or

Low-Temperature Synthesis of Superconducting Nanocrystalline MgB 2

DOE PAGES

Lu, Jun; Xiao, Zhili; Lin, Qiyin; ...

2010-01-01

Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 at temperatures as low as 450 ° C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

Silver nanoparticle release from commercially available plastic food containers into food simulants

NASA Astrophysics Data System (ADS)

Mackevica, Aiga; Olsson, Mikael Emil; Hansen, Steffen Foss

2016-01-01

Silver nanoparticles (AgNPs) are currently being used in many different kinds of consumer products in order to take advantage of their antimicrobial properties. However, the potential migration of silver nanoparticles into food and subsequent consumer exposure has hardly been addressed. In the current study, we investigated four brands of commercially available plastic food storage containers and measured the total amount of silver, particle size and number concentration, and the migration rates into three different food simulants (Milli-Q grade water, 10 % ethanol, and 3 % acetic acid) for 10 days at 40 °C. The experimental setup was made according to the European Commission Directive (EU 10/2011) for articles intended to be in contact with food. The total amount of silver in plastic containers and migration solutions was quantified by ICP-MS analysis, and the size of the migrated particles was investigated by single particle ICP-MS and TEM-EDS. The total mass and median size of released particulate Ag were generally highest in 3 % acetic acid for three out of four food container brands. The total content of silver in the containers varied from 13 to 42 µg/g. The highest migration was observed in the 3 % acetic acid food simulant for all four brands of containers, with total silver release up to 3.1 ng/cm2 after 10 days. In conclusion, the experimental results show that silver has the potential of migrating into food, especially when in contact with more acidic substances.

Characterisations of collagen-silver-hydroxyapatite nanocomposites

NASA Astrophysics Data System (ADS)

Ciobanu, C. S.; Popa, C. L.; Petre, C. C.; Jiga, G.; Trusca, R.; Predoi, D.

2016-05-01

The XRD analysis were performed to confirm the formation of hydroxyapatite structure in collagen-silver-hydroxyapatite nanocomposites. The molecular interaction in collagen-hydroxyapatite nanocomposites was highlighted by Fourier transform infrared spectroscopy (FTIR) analysis. The SEM showed a nanostructure of collagen-silverhydroxyapatite nanocomposites composed of nano needle-like particles in a veil with collagen texture. The presence of vibrational groups characteristics to the hydroxyapatite structure in collagen-silver-hydroxyapatite (AgHApColl) nanocomposites was investigated by FTIR.

The local strength of individual alumina particles

NASA Astrophysics Data System (ADS)

Pejchal, Václav; Fornabaio, Marta; Žagar, Goran; Mortensen, Andreas

2017-12-01

We implement the C-shaped sample test method and micro-cantilever beam testing to measure the local strength of microscopic, low-aspect-ratio ceramic particles, namely high-purity vapor grown α-alumina Sumicorundum® particles 15-30 μm in diameter, known to be attractive reinforcing particles for aluminum. Individual particles are shaped by focused ion beam micromachining so as to probe in tension a portion of the particle surface that is left unaffected by ion-milling. Mechanical testing of C-shaped specimens is done ex-situ using a nanoindentation apparatus, and in the SEM using an in-situ nanomechanical testing system for micro-cantilever beams. The strength is evaluated for each individual specimen using bespoke finite element simulation. Results show that, provided the particle surface is free of readily observable defects such as pores, twins or grain boundaries and their associated grooves, the particles can achieve local strength values that approach those of high-perfection single-crystal alumina whiskers, on the order of 10 GPa, outperforming high-strength nanocrystalline alumina fibers and nano-thick alumina platelets used in bio-inspired composites. It is also shown that by far the most harmful defects are grain boundaries, leading to the general conclusion that alumina particles must be single-crystalline or alternatively nanocrystalline to fully develop their potential as a strong reinforcing phase in composite materials.

Optimization for extracellular biosynthesis of silver nanoparticles by Penicillium aculeatum Su1 and their antimicrobial activity and cytotoxic effect compared with silver ions.

PubMed

Ma, Liang; Su, Wei; Liu, Jian-Xin; Zeng, Xiao-Xi; Huang, Zhi; Li, Wen; Liu, Zheng-Chun; Tang, Jian-Xin

2017-08-01

The present study addresses an eco-friendly and energy-saving method for extracellular biosynthesis of silver nanoparticles (AgNPs) using a cell free filtrate of the fungus strain Penicillium aculeatum Su1 as a reducing agent. Parametric optimization of the biosynthesis process demonstrated different effects on the size, distribution, yield, and synthesis rate of biosynthesized AgNPs. The transmission electron microscopy (TEM) measurements demonstrated that AgNPs were spherical or approximately spherical, with a size between 4 and 55nm. High-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) analyses indicated that AgNPs were nanocrystalline by nature, with the character of a face-centered cubic (fcc). Fourier transform infrared spectroscopy (FTIR) analysis confirmed the existence of protein molecules that acted as a reducing agent and a capping agent during the biosynthesis process. Furthermore, the biosynthesized AgNPs exhibited higher antimicrobial activity than silver ions against Gram negative bacteria, Gram positive bacteria and fungi. Compared with silver ions, the biosynthesized AgNPs presented higher biocompatibility toward human bronchial epithelial (HBE) cells and high cytotoxicity in a dose-dependent manner with an IC 50 of 48.73μg/mL toward A549 cells. These results demonstrate that Penicillium aculeatum Su1 is a potential bioresource that can be used to produce low-cost and eco-friendly AgNPs as efficient antimicrobial agent, drug delivery vehicle or anticancer drug for clinic treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of silver release predictions using PARFUME with results from the AGR-2 irradiation experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collin, Blaise P.; Demkowicz, Paul A.; Baldwin, Charles A.

2016-11-01

The PARFUME (PARticle FUel ModEl) code was used to predict silver release from tristructural isotropic (TRISO) coated fuel particles and compacts during the second irradiation experiment (AGR-2) of the Advanced Gas Reactor Fuel Development and Qualification program. The PARFUME model for the AGR-2 experiment used the fuel compact volume average temperature for each of the 559 days of irradiation to calculate the release of fission product silver from a representative particle for a select number of AGR-2 compacts and individual fuel particles containing either mixed uranium carbide/oxide (UCO) or 100% uranium dioxide (UO2) kernels. Post-irradiation examination (PIE) measurements were performedmore » to provide data on release of silver from these compacts and individual fuel particles. The available experimental fractional releases of silver were compared to their corresponding PARFUME predictions. Preliminary comparisons show that PARFUME under-predicts the PIE results in UCO compacts and is in reasonable agreement with experimental data for UO2 compacts. The accuracy of PARFUME predictions is impacted by the code limitations in the modeling of the temporal and spatial distributions of the temperature across the compacts. Nevertheless, the comparisons on silver release lie within the same order of magnitude.« less

High fluorescence emission silver nano particles coated with poly (styrene-g-soybean oil) graft copolymers: Antibacterial activity and polymerization kinetics.

PubMed

Hazer, Baki; Kalaycı, Özlem A

2017-05-01

Autoxidation of poly unsaturated fatty acids makes negative effect on foods. In this work, this negative effect was turned to a great advantage using autoxidized soybean oil as a macroperoxide nanocomposite initiator containing silver nano particles in free radical polymerization of vinyl monomers. The synthesis of soybean oil macro peroxide was carried out by exposing soybean oil to air oxygen with the presence of silver nanoparticles (Ag NPs) at room temperature. Autoxidized soybean oil macroperoxide containing silver nanoparticles (Agsbox) successfully initiated the free radical polymerization of styrene in order to obtain Polystyrene (PS)-g-soybean oil graft copolymer containing Ag NPs. Both autoxidized soybean oil and PS-g-sbox with Ag NPs showed a surface plasmon resonance and high fluorescence emission. Overall rate constant (K) of styrene polymerization initiated by autoxidized soybean oil macroperoxide with Ag NPs was found to be K=1.95.10 -4 Lmol -1 s -1 at 95°C. Antibacterial efficiency was observed in the PS-g-soybean oil graft copolymer film samples containing Ag NPs. 1 H NMR and GPC techniques were used for the structural analysis of the fractionated polymeric oils. Copyright © 2016 Elsevier B.V. All rights reserved.

Dendrite-Free Nanocrystalline Zinc Electrodeposition from an Ionic Liquid Containing Nickel Triflate for Rechargeable Zn-Based Batteries.

PubMed

Liu, Zhen; Cui, Tong; Pulletikurthi, Giridhar; Lahiri, Abhishek; Carstens, Timo; Olschewski, Mark; Endres, Frank

2016-02-18

Metallic zinc is a promising anode material for rechargeable Zn-based batteries. However, the dendritic growth of zinc has prevented practical applications. Herein it is demonstrated that dendrite-free zinc deposits with a nanocrystalline structure can be obtained by using nickel triflate as an additive in a zinc triflate containing ionic liquid. The formation of a thin layer of Zn-Ni alloy (η- and γ-phases) on the surface and in the initial stages of deposition along with the formation of an interfacial layer on the electrode strongly affect the nucleation and growth of zinc. A well-defined and uniform nanocrystalline zinc deposit with particle sizes of about 25 nm was obtained in the presence of Ni(II) . Further, it is shown that the nanocrystalline Zn exhibits a high cycling stability even after 50 deposition/stripping cycles. This strategy of introducing an inorganic metal salt in ionic liquid electrolytes can be considered as an efficient way to obtain dendrite-free zinc. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

PubMed

Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

2010-06-15

In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

Particle-Film Plasmons on Periodic Silver Film over Nanosphere (AgFON): A Hybrid Plasmonic Nanoarchitecture for Surface-Enhanced Raman Spectroscopy.

PubMed

Lee, Jiwon; Zhang, Qianpeng; Park, Seungyoung; Choe, Ayoung; Fan, Zhiyong; Ko, Hyunhyub

2016-01-13

Plasmonic systems based on particle-film plasmonic couplings have recently attracted great attention because of the significantly enhanced electric field at the particle-film gaps. Here, we introduce a hybrid plasmonic architecture utilizing combined plasmonic effects of particle-film gap plasmons and silver film over nanosphere (AgFON) substrates. When gold nanoparticles (AuNPs) are assembled on AgFON substrates with controllable particle-film gap distances, the AuNP-AgFON system supports multiple plasmonic couplings from interparticle, particle-film, and crevice gaps, resulting in a huge surface-enhanced Raman spectroscopy (SERS) effect. We show that the periodicity of AgFON substrates and the particle-film gaps greatly affects the surface plasmon resonances, and thus, the SERS effects due to the interplay between multiple plasmonic couplings. The optimally designed AuNP-AgFON substrate shows a SERS enhancement of 233 times compared to the bare AgFON substrate. The ultrasensitive SERS sensing capability is also demonstrated by detecting glutathione, a neurochemical molecule that is an important antioxidant, down to the 10 pM level.

Nanocrystalline LaOx/NiO composite as high performance electrodes for supercapacitors.

PubMed

Du, Guo; Zeng, Zifan; Xiao, Bangqing; Wang, Dengzhi; Yuan, Yuan; Zhu, Xiaohong; Zhu, Jiliang

2017-12-21

Nanocrystalline LaO x /NiO composite electrodes were synthesized via two types of facile cathodic electrodeposition methods onto nickel foam followed by thermal annealing without any binders. Scanning electron microscopy and transmission electron microscopy investigation revealed that LaO x nanocrystalline particles with an average diameter of 50 nm are uniformly distributed in the NiO layer or alternately deposited with the NiO layer onto the substrate. It is speculated that LaO x particles can participate in the faradaic reaction directly and offer more redox sites. Besides this, the unique Ni/La layered structure facilitates the diffusion of ions and retards the electrode polarization, thus leading to a better rate capability and cycling stability of NiO. As a result, the obtained electrodes display very competitive electrochemical performance (a specific capacitance of 1238 F g -1 at a current density of 0.5 A g -1 , excellent rate capability of 86% of the original capacitance at 10 A g -1 and excellent cycling stability of 93% capacitance after 10 000 cycles). In addition, asymmetric coin devices were assembled using LaO x /NiO as the positive electrode and active carbon as the negative electrode. The assembled asymmetric devices demonstrate a high energy density of 13.12 W h kg -1 at a power density of 90.72 W kg -1 .

Synthesis of positively charged hybrid PHMB-stabilized silver nanoparticles: the search for a new type of active substances used in plant protection products

NASA Astrophysics Data System (ADS)

Krutyakov, Yurii A.; Kudrinsky, Alexey A.; Gusev, Alexander A.; Zakharova, Olga V.; Klimov, Alexey I.; Yapryntsev, Alexey D.; Zherebin, Pavel M.; Shapoval, Olga A.; Lisichkin, Georgii V.

2017-07-01

Modern agriculture calls for a decrease in pesticide application, particularly in order to decrease the negative impact on the environment. Therefore the development of new active substances and plant protection products (PPP) to minimize the chemical load on ecosystems is a very important problem. Substances based on silver nanoparticles are a promising solution of this problem because of the fact that in correct doses such products significantly increase yields and decrease crop diseases while displaying low toxicity to humans and animals. In this paper we for the first time propose application of polymeric guanidine compounds with varying chain lengths (from 10 to 130 elementary links) for the design and synthesis of modified silver nanoparticles to be used as the basis of a new generation of PPP. Colloidal solutions of nanocrystalline silver containing 0.5 g l-1 of silver and 0.01-0.4 g l-1 of polyhexamethylene biguanide hydrochloride (PHMB) were obtained by reduction of silver nitrate with sodium borohydride in the presence of PHMB. The field experiment has shown that silver-containing solutions have a positive effect on agronomic properties of potato, wheat and apple. Also the increase in activity of such antioxidant system enzymes as peroxidase and catalase in the tissues of plants treated with nanosilver has been registered.

Silver nanoparticle-E. coli colloidal interaction in water and effect on E. coli survival.

PubMed

Dror-Ehre, A; Mamane, H; Belenkova, T; Markovich, G; Adin, A

2009-11-15

Silver nanoparticles exhibit antibacterial properties via bacterial inactivation and growth inhibition. The mechanism is not yet completely understood. This work was aimed at elucidating the effect of silver nanoparticles on inactivation of Escherichia coli, by studying particle-particle interactions in aqueous suspensions. Stable, molecularly capped, positively or negatively charged silver nanoparticles were mixed at 1 to 60microgmL(-1) with suspended E. coli cells to examine their effect on inactivation of the bacteria. Gold nanoparticles with the same surfactant were used as a control, being of similar size but made up of a presumably inert metal. Log reduction of 5log(10) and complete inactivation were obtained with the silver nanoparticles while the gold nanoparticles did not show any inactivation ability. The effect of molecularly capped nanoparticles on E. coli survival was dependent on particle number. Log reduction of E. coli was associated with the ratio between the number of nanoparticles and the initial bacterial cell count. Electrostatic attraction or repulsion mechanisms in silver nanoparticle-E. coli cell interactions did not contribute to the inactivation process.

Silver nanoparticles-coated glass frits for silicon solar cells

NASA Astrophysics Data System (ADS)

Li, Yingfen; Gan, Weiping; Li, Biyuan

2016-04-01

Silver nanoparticles-coated glass frit composite powders for silicon solar cells were prepared by electroless plating. Silver colloids were used as the activating agent of glass frits. The products were characterized by X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry. The characterization results indicated that silver nanoparticles with the melting temperature of 838 °C were uniformly deposited on glass frit surface. The particle size of silver nanoparticles could be controlled by adjusting the [Ag(NH3)2]NO3 concentration. The as-prepared composite powders were applied in the front side metallization of silicon solar cells. Compared with those based on pure glass frits, the solar cells containing the composite powders had the denser silver electrodes and the better silver-silicon ohmic contacts. Furthermore, the photovoltaic performances of solar cells were improved after the electroless plating.

SERS and DFT study of p-hydroxybenzoic acid adsorbed on colloidal silver particles.

PubMed

Chen, Y; Chen, S J; Li, S; Wei, J J

2015-10-16

In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.

Template-assisted formation of microsized nanocrystalline CeO2 tubes and their catalytic performance in the carboxylation of methanol

PubMed Central

Naumann, Meike; Schäfer, Christian; Brandner, Armin; Hofmann, Heiko J; Claus, Peter

2011-01-01

Summary Polymethylmethacrylate (PMMA)/ceria composite fibres were synthesized by using a sequential combination of polymer electrospinning, spray-coating with a sol, and a final calcination step to yield microstructured ceria tubes, which are composed of nanocrystalline ceria particles. The PMMA template is removed from the organic/inorganic hybrid material by radio frequency (rf) plasma etching followed by calcination of the ceramic green-body fibres. Microsized ceria (CeO2) tubes, with a diameter of ca. 0.75 µm, composed of nanocrystalline agglomerated ceria particles were thus obtained. The 1-D ceramic ceria material was characterized by X-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV–vis and photoluminescence spectroscopy (PL), as well as thermogravimetric analysis (TGA). Its catalytic performance was studied in the direct carboxylation of methanol with carbon dioxide leading to dimethyl carbonate [(CH3O)2CO, DMC], which is widely employed as a phosgene and dimethyl sulfate substitute, and as well as a fuel additive. PMID:22259761

Diffraction Studies of the Atomic Vibrations of Bulk and Surface Atoms in the Reciprocal and Real Spaces of Nanocrystalline SiC

NASA Technical Reports Server (NTRS)

Stelmakh, S.; Grzanka, E.; Weber, H.-P.; Vogel, S.; Palosz, B.; Palosz, B.

2004-01-01

To describe and evaluate the vibrational properties of nanoparticles it is necessary to distinguish between the surface and the core of the particles. Theoretical calculations show that vibrational density of states of the inner atoms of nanograins is similar to bulk material but shifted to higher energies which can be explained by the fact that the gain core is stressed (hardened) due to the presence of internal pressure. Theoretical calculations also show that there is a difference between vibrational properties of a crystal lattice of the grain interior in isolated particles and in a dense (sintered) nanocrystalline material. This is probably due to a coupling of the modes inside the grains via the grain boundaries in dense nanocrystalline bodies. We examined strains present in the surface shell based on examination of diamond and Sic nanocrystals in reciprocal (Bragg-type scattering) and real (PDF analysis) space analysis of neutron diffraction data. Recently we examined the atomic thermal motions in nanocrystalline Sic based on the assumption of a simple Einstein model for uncorrelated atomic notions. According to this model, the Bragg intensity is attenuated as a function of scattering angle by the Debye-Waller factor. Based on this assumption overall temperature factors were determined from the Wilson plots.

Protein-Modified-Paramagnetic-Particles as a Tool for Detection of Silver(I) Ions

NASA Astrophysics Data System (ADS)

Kizek, R.; Krizkova, S.; Adam, V.; Huska, D.; Hubalek, J.; Trnkova, L.

2009-04-01

In a number of published articles the toxic effect of silver(I) ions on aquatic organisms is described. Silver(I) ions in aquatic environment are stable in a wide range of pH. Under alkali pH AgOH and Ag(OH)2- can be formed. However, in water environment there are many compounds to interact with silver(I) ions. The most important ones are chloride anions, which forms insoluble precipitate with silver(I) ions (AgCl). The insoluble silver containing compounds do not pose any threat to aquatic organisms. Toxicity of silver ions is probably caused by their very good affinity to nucleic acids and also proteins. The binding into active enzyme site leads to the expressive enzyme reaction inhibition. Silver(I) ions are into living environment introduced thanks to anthropogenic activities. They easily contaminate atmosphere as well as aquatic environment or soils. Several authors described using of carbon electrode as working electrode for determination of silver. Recently, we have suggested heavy metal biosensor based on interaction of metal ions with low molecular mass protein called metallothionein (MT), which was adsorbed on the surface of hanging mercury drop electrode (HMDE). The biosensor was successfully used for detection of cadmium(II) and zinc(II) ions, cisplatin, cisplatin-DNA adducts and palladium(II) ions. Due to the convincing results with MT as biological component we report on suggesting of heavy metal biosensor based on immobilization of metallothionein (MT) on the surface of carbon paste electrode (CPE) via MT-antibodies. Primarily we studied of basic electrochemical behaviour of MT at surface of carbon paste electrode by using of square wave voltammetry (SWV). Detection limit (3 S/N) for MT was evaluated as 0.1 μg/ml. After that we have evaluated the electroactivity of MT at surface of SWV, we aimed our attention on the way of capturing of MT on the surface of CPE. We choose antibody against MT obtained from chicken eggs for these purposes. Antibodies

Enhancement of the stability of silver nanoparticles synthesized using aqueous extract of Diospyros discolor Willd. leaves using polyvinyl alcohol

NASA Astrophysics Data System (ADS)

Ardani, H. K.; Imawan, C.; Handayani, W.; Djuhana, D.; Harmoko, A.; Fauzia, V.

2017-04-01

Biosynthesis of silver nanoparticles is recently attracting considerable attention because of it reduces the environmental impact and already used in numerous applications. However, the disadvantages such as easy aggregation and instability properties, prevent its’ application. In this papers, biosynthesis of silver nanoparticles using aqueous extract of Diospyros discolor Willd. leaves have been prepared. The effect of biosynthesis variables, like ratio of reactants and reduction time on the particle size distribution, stability, and morphology of the silver nanoparticles were investigated. The resulted silver nanoparticles were characterized using UV spectroscopy, Transmission Electron Microscopy, and Particles Size Analyzer. Polyvinyl alcohol (PVA) was used to enhance the stability of the silver nanoparticles. Silver nanoparticles modification with 1% PVA concentration has produced a better characteristic of particle size distribution compared to the original silver nanoparticles, from highly polydisperse into moderately disperse. The results of the Zetta potential measurement also confirmed the increase stability of cluster distribution in the colloidal Ag/PVA compared to the original Ag.

Preparation and characterization of silver nanoparticles homogenous thin films

NASA Astrophysics Data System (ADS)

Hegazy, Maroof A.; Borham, E.

2018-06-01

The wet chemical method by metal salt reduction has been widely used to synthesize nanoparticles. Accordingly the silver nitrate used as silver precursor and sodium borohydrate as reduction agent. The silver nanoparticles were characterized by different characterization techniques including UV-VIS spectrometry, Transmission electron microscope (TEM), and Zeta potential technique. Thin films of the colloidal solution were fabricated using direct precipitation technique on ITO glass, silicon substrate and commercial glass substrate and characterized by imaging technique. The absorption peak of the silver nanoparticles colloidal solution was around 400 nm. The TEM images indicate that the silver nanoparticles had spherical shape and their sizes were from 10 to 17 nm. The particle size of the silver nanoparticles was confirmed by Zeta potential technique. The imaging technique indicated that the homogeneous distribution of the colloidal silver solution thin film on the silicon substrate was stronger than the ITO glass and inhomogeneous film was emerged on the commercial glass.

Speciation Matters: Bioavailability of Silver and Silver Sulfide Nanoparticles to Alfalfa (Medicago sativa).

PubMed

Stegemeier, John P; Schwab, Fabienne; Colman, Benjamin P; Webb, Samuel M; Newville, Matthew; Lanzirotti, Antonio; Winkler, Christopher; Wiesner, Mark R; Lowry, Gregory V

2015-07-21

Terrestrial crops are directly exposed to silver nanoparticles (Ag-NPs) and their environmentally transformed analog silver sulfide nanoparticles (Ag2S-NPs) when wastewater treatment biosolids are applied as fertilizer to agricultural soils. This leads to a need to understand their bioavailability to plants. In the present study, the mechanisms of uptake and distribution of silver in alfalfa (Medicago sativa) were quantified and visualized upon hydroponic exposure to Ag-NPs, Ag2S-NPs, and AgNO3 at 3 mg total Ag/L. Total silver uptake was measured in dried roots and shoots, and the spatial distribution of elements was investigated using transmission electron microscopy (TEM) and synchrotron-based X-ray imaging techniques. Despite large differences in release of Ag(+) ions from the particles, Ag-NPs, Ag2S-NPs, and Ag(+) became associated with plant roots to a similar degree, and exhibited similarly limited (<1%) amounts of translocation of silver into the shoot system. X-ray fluorescence (XRF) mapping revealed differences in the distribution of Ag into roots for each treatment. Silver nanoparticles mainly accumulated in the (columella) border cells and elongation zone, whereas Ag(+) accumulated more uniformly throughout the root. In contrast, Ag2S-NPs remained largely adhered to the root exterior, and the presence of cytoplasmic nano-SixOy aggregates was observed. Exclusively in roots exposed to particulate silver, NPs smaller than the originally dosed NPs were identified by TEM in the cell walls. The apparent accumulation of Ag in the root apoplast determined by XRF, and the presence of small NPs in root cell walls suggests uptake of partially dissolved NPs and translocation along the apoplast.

Electrochemical synthesis, characterisation and phytogenic properties of silver nanoparticles

NASA Astrophysics Data System (ADS)

Singaravelan, R.; Bangaru Sudarsan Alwar, S.

2015-12-01

This work exemplifies a simple and rapid method for the synthesis of silver nanodendrite with a novel electrochemical technique. The antibacterial activity of these silver nanoparticles (Ag NPs) against pathogenic bacteria was investigated along with the routine study of optical and spectral characterisation. The optical properties of the silver nanoparticles were characterised by diffuse reflectance spectroscopy. The optical band gap energy of the electrodeposited Ag NPs was determined from the diffuse reflectance using Kubelka-Munk formula. X-ray diffraction (XRD) studies were carried out to determine the crystalline nature of the silver nanoparticles which confirmed the formation of silver nanocrystals. The XRD pattern revealed that the electrodeposited Ag NPs were in the cubic geometry with dendrite preponderance. The average particle size and the peak broadening were deliberated using Debye-Scherrer equation and lattice strain due to the peak broadening was studied using Williamson-Hall method. Surface morphology of the Ag NPs was characterised by high-resolution scanning electron microscope and the results showed the high degree of aggregation in the particles. The antibacterial activity of the Ag NPs was evaluated and showed unprecedented level antibacterial activity against multidrug resistant strains such as Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumonia and Escherichia coli in combination with Streptomycin.

Phyto-synthesis of silver nanoscale particles using Morinda citrifolia L. and its inhibitory activity against human pathogens.

PubMed

Sathishkumar, Gnanasekar; Gobinath, Chandrakasan; Karpagam, Karuppiah; Hemamalini, Vedagiri; Premkumar, Kumpati; Sivaramakrishnan, Sivaperumal

2012-06-15

Leaf extract of Morinda citrifolia L. was assessed for the synthesis of silver nanoscale particles under different temperature and reaction time. Synthesized nanoscale (MCAgNPs) particles were confirmed by analysing the excitation of surface plasmon resonance (SPR) using UV-visible spectrophotometer at 420 nm. Further SEM, HRTEM analysis confirmed the range of particle size between 10 and 60 nm and SEAD pattern authorizes the face centered cubic (fcc) crystalline nature of the MCAgNPs. Fourier transform infrared spectrum (FTIR) of synthesized MCAgNPs confirms the presence of high amount of phenolic compounds in the plant extract which may possibly influence the reduction process and stabilization of nanoparticles. Further, inhibitory activity of MCAgNPs and plant extract were tested against human pathogens like Eschericia coli, Pseudomonas aeroginosa, Klebsiella pneumoniae, Enterobacter aerogenes, Bacillus cereus and Enterococci sp. The results indicated that the MCAgNPs showed moderate inhibitory actions against human pathogens than crude plant extract, demonstrating its antimicrobial value against pathogenic diseases. Copyright © 2012 Elsevier B.V. All rights reserved.

Magnetic properties of FeCuNbSiB nanocrystalline alloy powder cores using ball-milled powder

NASA Astrophysics Data System (ADS)

Kim, G. H.; Noh, T. H.; Choi, G. B.; Kim, K. Y.

2003-05-01

Cold-pressed nanocrystalline powder cores were fabricated using powders of nanocrystalline ribbons which were ball milled for short time. Their magnetic properties at high frequency were measured. The powder size ranges from 20 to 850 μm and the contents of the glass binder are between 1 and 8 wt %. For cores composed of large particles of 300-850 μm with 5 wt % glass binder, we obtained a stable permeability of 100 up to 800 kHz, a maximum level 31 of quality factor at frequency of 50 kHz, and 320 mW/cm3 core loss at f=50 kHz and Bm=0.1 T. This is mainly due to the good soft magnetic properties of the powders and the higher insulation of powder cores which cause low eddy current losses.

Spectroscopic study of surface enhanced Raman scattering of caffeine on borohydride-reduced silver colloids

NASA Astrophysics Data System (ADS)

Chen, Xiaomin; Gu, Huaimin; Shen, Gaoshan; Dong, Xiao; Kang, Jian

2010-06-01

The surface enhanced Raman scattering (SERS) of caffeine on borohydride-reduced silver colloids system under different aqueous solution environment has been studied in this paper. The relative intensity of SERS of caffeine significantly varies with different concentrations of sodium chloride and silver particles. However, at too high or too low concentration of sodium chloride and silver particle, the enhancement of SERS spectra is not evident. The SERS spectra of caffeine suggest that the contribution of the charge transfer mechanism to SERS may be dominant. The chloride ions can significantly enhance the efficiency of SERS, while the enhancement is selective, as the efficiency in charge transfer enhancement is higher than in electromagnetic enhancement. Therefore, it can be concluded that the active site of chloride ion locates on the bond between the caffeine and the silver surface. In addition, the SERS spectra of caffeine on borohydride-reduced and citrate-reduced silver colloids are different, which may be due to different states caffeine adsorbed on silver surface under different silver colloids.

Nanostructured silver sulfide: synthesis of various forms and their application

NASA Astrophysics Data System (ADS)

Sadovnikov, S. I.; Rempel, A. A.; Gusev, A. I.

2018-04-01

The results of experimental studies on nanostructured silver sulfide are analyzed and generalized. The influence of small particle size on nonstoichiometry of silver sulfide is discussed. Methods for the synthesis of various forms of nanostructured Ag2S including nanopowders, stable colloidal solutions, quantum dots, core–shell nanoparticles and heteronanostructures are described. The advantages and drawbacks of different synthetic procedures are analyzed. Main fields of application of nanostructured silver sulfide are considered. The bibliography includes 184 references.

Nanocrystalline heterojunction materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2003-07-15

Mesoporous nanocrystalline titanium dioxide heterojunction materials are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

In-vitro free radical scavenging activity of biosynthesized gold and silver nanoparticles using Prunus armeniaca (apricot) fruit extract

NASA Astrophysics Data System (ADS)

Dauthal, Preeti; Mukhopadhyay, Mausumi

2013-01-01

In-vitro free radical scavenging activity of biosynthesized gold (Au-NPs) and silver (Ag-NPs) nanoparticles was investigated in the present study. Natural precursor Prunus armeniaca (apricot) fruit extract was used as a reducing agent for the nanoparticle synthesis. The free radical scavenging activity of the nanoparticles were observed by modified 1,1'-diphynyl-2-picrylhydrazyl, DPPH and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid), ABTS assay. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, dynamic light scattering, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy, and fourier transform infrared spectroscopy (FTIR). Appearance of optical absorption peak at 537 nm (2.20 keV) and 435 nm (3 keV) within 0.08 and 0.5 h of reaction time was confirmed the presence of metallic Au and Ag nanoclusters, respectively. Nearly spherical nanoparticles with majority of particle below 20 nm (TEM) for both Au-NPs and Ag-NPs were synthesized. XRD pattern confirmed the existence of pure nanocrystalline Au-NPs while few additional peaks in the vicinity of fcc silver-speculated crystallization of metalloproteins of fruit extract on the surface of the Ag-NPs and vice versa. FTIR spectra was supported the role of amino acids of protein/enzymes of fruit extract for synthesis and stabilization of nanoparticles. Dose-dependent scavenging activity was observed for Au-NPs and Ag-NPs in both DPPH and ABTS in-vitro assay. 50 % scavenging activity for DPPH were 11.27 and 16.18 mg and for ABTS 3.40 and 7.12 mg with Au-NPs and Ag-NPs, respectively.

Synthesis of Nano-Crystalline Gamma-TiAl Materials

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Vasquez, Peter

2003-01-01

One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

Interference of Steroidogenesis by Gold Nanorod Core/Silver Shell Nanostructures: Implications for Reproductive Toxicity of Silver Nanomaterials.

PubMed

Jiang, Xiumei; Wang, Liming; Ji, Yinglu; Tang, Jinglong; Tian, Xin; Cao, Mingjing; Li, Jingxuan; Bi, Shuying; Wu, Xiaochun; Chen, Chunying; Yin, Jun-Jie

2017-03-01

As a widely used nanomaterial in daily life, silver nanomaterials may cause great concern to female reproductive system as they are found to penetrate the blood-placental barrier and gain access to the ovary. However, it is largely unknown about how silver nanomaterials influence ovarian physiology and functions such as hormone production. This study performs in vitro toxicology study of silver nanomaterials, focusing especially on cytotoxicity and steroidogenesis and explores their underlying mechanisms. This study exposes primary rat granulosa cells to gold nanorod core/silver shell nanostructures (Au@Ag NRs), and compares outcomes with cells exposed to gold nanorods. The Au@Ag NRs generate more reactive oxygen species and reduce mitochondrial membrane potential and less production of adenosine triphosphate. Au@Ag NRs promote steroidogenesis, including progesterone and estradiol, in a time- and dose-dependent manner. Chemical reactivity and transformation of Au@Ag NRs are then studied by electron spin resonance spectroscopy and X-ray absorption near edge structure, which analyze the generation of free radical and intracellular silver species. Results suggest that both particle-specific activity and intracellular silver ion release of Au@Ag NR contribute to the toxic response of granulosa cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of silver nanoparticles in virgin coconut oil using laser ablation.

PubMed

Zamiri, Reza; Azmi, B Z; Sadrolhosseini, Amir Reza; Ahangar, Hossein Abbastabar; Zaidan, A W; Mahdi, M A

2011-01-07

Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10(-8), 1.6 × 10(-8), 2.4 × 10(-8), respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method.

Influence of Dispersant and Heat Treatment on the Morphology of Nanocrystalline Hydroxyapatite

NASA Astrophysics Data System (ADS)

Pan, Yusong; Xiong, Dangsheng

2010-10-01

Natural biological hard tissues are biocomposites of proteins and hydroxyapatite (HA) with superior strength. Nanometer scale HAp is the key material to manufacture bone substitute. In this work, nano-sized HA particles were synthesized by a wet method using orthophosphoric acid and calcium hydroxide as raw materials. The prepared nanocrystalline HAp was characterized for its phase purity and nano-scale morphological structure by XRD, TEM, and FTIR. The influences of heat treatment temperature and dispersant on the properties of HAp were also investigated. The results indicated that nano-particles were pure single-phase HAp with a diameter of 25-70 nm and length of 50-180 nm depending on heat treatment temperature. The morphology and crystallite size of HAp change with heat treatment temperature. After heat treating, the crystallinity of these nano-particles increased and its morphology transformed from needle-like to sphere-like structure. The dispersant is beneficial to prevent the growth of HA particles and provide a uniform particle size distribution. Moreover, the HAp tends to form small agglomerates in the absence of dispersant.

Limitation of biocompatibility of hydrated nanocrystalline hydroxyapatite

NASA Astrophysics Data System (ADS)

Minaychev, V. V.; Teleshev, A. T.; Gorshenev, V. N.; Yakovleva, M. A.; Fomichev, V. A.; Pankratov, A. S.; Menshikh, K. A.; Fadeev, R. S.; Fadeeva, I. S.; Senotov, A. S.; Kobyakova, M. I.; Yurasova, Yu B.; Akatov, V. S.

2018-04-01

Nanostructured hydroxyapatite (HA) in the form of hydrated paste is considered to be a promising material for a minor-invasive surgical curing of bone tissue injure. However questions about adhesion of cells on this material and its biocompatibility still remain. In this study biocompatibility of paste-formed nanosized HA (nano-HA) by in vitro methods is investigated. Nano-HA (particles sized about 20 nm) was synthesized under conditions of mechano-acoustic activation of an aqueous reaction mixture of ammonium hydrophosphate and calcium nitrate. It was ascertained that nanocrystalline paste was not cytotoxic although limitation of adhesion, spreading and growth of the cells on its surface was revealed. The results obtained point on the need of modification of hydrated nano-HA in the aims of increasing its biocompatibility and osteoplastic potential.

Improvement of diamond-like carbon electrochemical corrosion resistance by addition of nanocrystalline diamond.

PubMed

Marciano, F R; Almeida, E C; Bonetti, L F; Corat, E J; Trava-Airoldi, V J

2010-02-15

Nanocrystalline diamond (NCD) particles were incorporated into diamond-like carbon (DLC) films in order to investigate NCD-DLC electrochemical corrosion resistance. The films were grown over 304 stainless steel using plasma-enhanced chemical vapor deposition. NCD particles were incorporated into DLC during the deposition process. The investigation of NCD-DLC electrochemical corrosion behavior was performed using potentiodynamic polarization against NaCl. NCD-DLC films presented more negative corrosion potential and lower anodic and cathodic current densities. The electrochemical analysis indicated that NCD-DLC films present superior impedance and polarization resistance compared to the pure DLC, which indicate that they are promising corrosion protective coatings in aggressive solutions. Copyright 2009 Elsevier Inc. All rights reserved.

Green Synthesis of Robust, Biocompatible Silver Nanoparticles Using Garlic Extract

PubMed Central

Von White, Gregory; Kerscher, Petra; Brown, Ryan M.; Morella, Jacob D.; McAllister, William; Dean, Delphine; Kitchens, Christopher L.

2012-01-01

This paper details a facile approach for the synthesis of stable and monodisperse silver nanoparticles performed at ambient/low temperature where Allium sativum (garlic) extract functions as the silver salt reducing agent during nanoparticle synthesis as well as the post-synthesis stabilizing ligands. Varying the synthesis conditions provides control of particle size, size-distribution, and kinetics of particle formation. Infrared spectroscopy, energy dispersive x-ray chemical analysis, and high performance liquid chromatography indicated that the carbohydrates present in the garlic extract are the most likely nanoparticle stabilizing chemistry. The synthesized silver nanoparticles also demonstrate potential for biomeical applications, owing to the 1) enhanced stability in biological media, 2) resistance to oxidation by the addition of H2O2, 3) ease and scalability of synthesis, and 4) lack of harsh chemicals required for synthesis. Cytotoxicity assays indicated no decrease in cellular proliferation for vascular smooth muscle cells and 3T3 fibroblasts at a concentration of 25 μg/ml, confirming that garlic extract prepared silver nanoparticles are ideal candidates for future experimentation and implementation into biomedical applications. PMID:24683414

Green Synthesis of Robust, Biocompatible Silver Nanoparticles Using Garlic Extract.

PubMed

Von White, Gregory; Kerscher, Petra; Brown, Ryan M; Morella, Jacob D; McAllister, William; Dean, Delphine; Kitchens, Christopher L

2012-01-01

This paper details a facile approach for the synthesis of stable and monodisperse silver nanoparticles performed at ambient/low temperature where Allium sativum (garlic) extract functions as the silver salt reducing agent during nanoparticle synthesis as well as the post-synthesis stabilizing ligands. Varying the synthesis conditions provides control of particle size, size-distribution, and kinetics of particle formation. Infrared spectroscopy, energy dispersive x-ray chemical analysis, and high performance liquid chromatography indicated that the carbohydrates present in the garlic extract are the most likely nanoparticle stabilizing chemistry. The synthesized silver nanoparticles also demonstrate potential for biomeical applications, owing to the 1) enhanced stability in biological media, 2) resistance to oxidation by the addition of H 2 O 2 , 3) ease and scalability of synthesis, and 4) lack of harsh chemicals required for synthesis. Cytotoxicity assays indicated no decrease in cellular proliferation for vascular smooth muscle cells and 3T3 fibroblasts at a concentration of 25 μg/ml, confirming that garlic extract prepared silver nanoparticles are ideal candidates for future experimentation and implementation into biomedical applications.

Preparation of starch stabilized silver nanoparticles with spatial self-phase modulation properties by laser ablation technique

NASA Astrophysics Data System (ADS)

Zamiri, Reza; Azmi, B. Z.; Darroudi, Majid; Sadrolhosseini, Amir R.; Husin, M. S.; Zaidan, A. W.; Mahdi, M. A.

2011-01-01

Silver nanoparticles inside the starch solution have been successfully fabricated by laser ablation of a silver plate immersed in starch solution. The ablation has been done using a Q-switched Nd:YAG laser at 10 Hz repetition rate. The starch solution allows for the formation of silver nanoparticles with uniform particle diameters and well dispersed. The ablation was performed at different time durations to study the influence of the laser ablation time on efficiency of particle formation and sizes. The Spatial Self-phase modulation phenomena which can determine the nonlinear optical property of the samples were also investigated for starch solutions containing silver nanoparticles.

Silver Nanoparticle Oligonucleotide Conjugates Based on DNA with Triple Cyclic Disulfide Moieties

PubMed Central

Lee, Jae-Seung; Lytton-Jean, Abigail K. R.; Hurst, Sarah J.; Mirkin, Chad A.

2011-01-01

We report a new strategy for preparing silver nanoparticle oligonucleotide conjugates that are based upon DNA with cyclic disulfide-anchoring groups. These particles are extremely stable and can withstand NaCl concentrations up to 1.0 M. When silver nanoparticles functionalized with complementary sequences are combined, they assemble to form DNA-linked nanoparticle networks. This assembly process is reversible with heating and is associated with a red-shifting of the particle surface plasmon resonance and a concomitant color change from yellow to pale red. Analogous to the oligonucleotide-functionalized gold nanoparticles, these particles also exhibit highly cooperative binding properties with extremely sharp melting transitions. This work is an important step towards being able to use silver nanoparticle oligonucleotide conjugates for a variety of purposes, including molecular diagnostic labels, synthons in programmable materials synthesis approaches, and functional components for nanoelectronic and plasmonic devices. PMID:17571909

Effects of the surface modification of silver nanoparticles on the surface-enhanced Raman spectroscopy of methylene blue for borohydride-reduced silver colloid

NASA Astrophysics Data System (ADS)

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

2010-12-01

The paper further investigated the relationship between the modification of the surface chemistry and the enhancement mechanisms of borohydride-reduced silver particles (BRSC). The bands of residual ions die down while the anomalous bands increase gradually with the increasing of the concentration of Cl - and Br -. It means the residual ions are displaced gradually by the added Cl - or Br - and the two halides can lead to the aggregation of the BRSC to a certain extent. However, the most strongly binding anions - I -, cannot cause any aggregation of silver particles. From the detection of methylene blue (MB), the relationship between the modification of silver surface chemistry and the enhancement mechanisms was discussed. Chloride gives the greatest enhancement while the iodide gives the lowest enhancement among the different kinds of anions. There are also some anomalous bands in the SERS spectra of MB, and these anomalous bands were given rational explanation in this paper.

Application of micro- and nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Sotnikova, Yu S.; Demina, T. S.; Istomin, A. V.; Goncharuk, G. P.; Grandfils, Ch; Akopova, T. A.; Zelenetskii, A. N.; Babayevsky, P. G.

2018-04-01

Micro- and nanocrystalline forms of cellulose were extracted from flax stalks and evaluated in terms of their applicability for various materials science tasks. It was revealed that both form of cellulose had anisometric morphology with length of 27.1 μm and 159 nm; diameter of 8.7 μm and 85 nm, respectively. They were used as reinforcing fillers for fabrication of composite films based on hydroxyethylcellulose. Film-forming and mechanical properties of the composite materials were significantly varied in dependence on filler content (0–10 wt.%) and size. As a second option of micro- and nanocrystalline cellulose application, a study of their effectiveness as stabilizing agents for oil/water Pickering emulsions was carried out. In contrast to micron-sized cellulose the nanocrystalline form appeared to be successful in the process of CH2Cl2/water interface stabilization and fabrication of polylactide microparticles via oil/water Pickering emulsion solvent evaporation technique.

Fabrication, characterization, and thermal property evaluation of silver nanofluids

PubMed Central

2014-01-01

Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively. PMID:25489293

Investigations of Nanocrystalline Alloy Electrospark Coating Made of Nanocrystalline Alloy Based on 5БДCP Ferrum

NASA Astrophysics Data System (ADS)

Kolomeichenko, A. V.; Kuznetsov, I. S.; Izmaylov, A. Yu; Solovyev, R. Yu; Sharifullin, S. N.

2017-09-01

The article describes the properties of wear resistant electrospark coating made of nanocrystalline alloy of type 5БДCP (Finemet). It is proved that electrospark coating has nanocrystalline structure which is like amorphous matrix with nanocrystals α - Fe. Coating thickness is 33 μm, micro-hardness is 8461 - 11357 MPa, wear resistance is 0,55×104s/g. Coating ofnanocrystalline alloy of type 5БДCP can be used to increase wear resistance of machinery working surfaces.

Configuration of twins in glass-embedded silver nanoparticles of various origin

NASA Astrophysics Data System (ADS)

Hofmeister, H.; Dubiel, M.; Tan, G. L.; Schicke, K.-D.

2005-09-01

Structural characterization using high resolution electron microscopy and diffractogram analysis of silver nanoparticles embedded in glass by various routes of fabrication was aimed at revealing the characteristic features of twin faults occuring in such particles. Nearly spherical silver nanoparticles well below 10 nm size embedded in commercial soda-lime silicate float glass have been fabricated either by silver/sodium ion exchange or by Ag+ ion implantation. Twinned nanoparticles, besides single crystalline species, have frequently been observed for both fabrication routes, mainly at sizes above 5 nm, but also at smaller sizes, even around 1 nm. The variety of particle forms comprises single crystalline particles of nearly cuboctahedron shape, particles containing single twin faults, and multiply twinned particles containing parallel twin lamellae, or cyclic twinned segments arranged around axes of fivefold symmetry. Parallel twinning is distinctly favoured by ion implantation whereas cyclic twinning preferably occurs upon ion exchange processing. Regardless of single or repeated twinning, parallel or cyclic twin arrangement, one may classify simple twin faults of regular atomic configuration and compound twin faults whose irregular configuration consists of additional planar defects like associated stacking faults or secondary twin faults. Besides, a particular superstructure composed of parallel twin lamellae of only three atomic layers thickness is observed.

Sonochemical Synthesis of Silver Nanoparticles Using Starch: A Comparison

PubMed Central

Smita, Kumari; Cumbal, Luis; Debut, Alexis; Pathak, Ravinandan Nath

2014-01-01

A novel approach was applied to synthesize silver nanoparticles using starch under sonication. Colloidal silver nanoparticles solution exhibited an increase of absorption from 420 to 440 nm with increase starch quantity. Transmission electron microscopy followed by selected area electron diffraction pattern analysis indicated the formation of spherical, polydispersed, amorphous, silver nanoparticles of diameter ranging from 23 to 97 nm with mean particle size of 45.6 nm. Selected area electron diffraction (SAED) confirmed partial crystalline and amorphous nature of silver nanoparticles. Silver nanoparticles synthesized in this manner can be used for synthesis of 2-aryl substituted benzimidazoles which have numerous biomedical applications. The optimized reaction conditions include 10 ml of 1 mM AgNO3, 25 mg starch, 11 pH range, and sonication for 20 min at room temperature. PMID:24587771

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

NASA Astrophysics Data System (ADS)

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

2013-09-01

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

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

DTIC Science & Technology

2014-11-01

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and...3. DATES COVERED (From - To) August 2014 4. TITLE AND SUBTITLE Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by

Optical slicing and 3-D characterization of hippocampal capillaries in the rat visualized by autometallographic silver enhancement of colloidal gold particles.

PubMed

Andreasen, A; Danscher, G

1997-10-01

In order to visualize the vascular system of the rat brain, 10 Wistar rats were perfused transcardially with glutaraldehyde and a 40 degrees C gold-gelatine solution. The brains were post-fixed with glutaraldehyde and vibratomized into 100-micron-thick slices, and the gold particles were developed by autometallography. In this way, the colloidal gold particles in the vessels became encased in silver and thereby made visible. The developed gold staining is stable and does not interfere with further dehydration and counterstaining. Images were frame grabbed during optical slicing, and classic stereograms and 'shadow' 3-D images were produced. We found a high variation of capillary density in the hippocampal region reflecting known subregional structures. The silver-enhanced vessels acted as natural markers and made it possible to study and measure aspects of the complexity of dehydration and staining artifacts. We found a non-linear shrinking of 13-17% in the x- and y-directions and a spatial shrinking up to 50% in some regions after the dehydration and staining process. This observation may be of interest not only in relation to tissue subjected to this fixation protocol but also to other fixation procedures. The gold-gelatine autometallographic technique and the present stereograms can release data for stereological use as well.

Nanocrystalline (U0.5Ce0.5)O2±x solid solutions through citrate gel-combustion

NASA Astrophysics Data System (ADS)

Maji, D.; Ananthasivan, K.; Venkata Krishnan, R.; Balakrishnan, S.; Amirthapandian, S.; Joseph, Kitheri; Dasgupta, Arup

2018-04-01

Nanocrystalline powders of (U0.5Ce0.5)O2±x solid solutions were synthesized in bulk (100-200 g) through the citrate gel combustion. The fuel (citric acid) to oxidant (nitrate) mole ratio (R) was varied from 0.1 to 1.0. Two independent lots of the products obtained through the gel-combustion were calcined at 973 K in air and in a mixture of argon containing 8% H2 respectively. All these powders were characterized for their bulk density, X-ray crystallite size, specific surface area, size distribution of the particles, porosity as well as residual carbon. The morphology and microstructures of these powders were studied by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Nanocrystalline single phase fluorite solid solutions having a typical crystallite size of about (7-15 nm) were obtained. These powders were highly porous comprising cuboidal flaky agglomerates. The combustion mixture with an 'R' value of 0.25 was found to undergo volume combustion and was found to yield a product that was distinctly different. The systematic investigation on synthesis and characterization of nanocrystalline UCeO2 is reported for the first time.

Nanodimensional and Nanocrystalline Apatites and Other Calcium Orthophosphates in Biomedical Engineering, Biology and Medicine

PubMed Central

Dorozhkin, Sergey V.

2009-01-01

Recent developments in biomineralization have already demonstrated that nanosized particles play an important role in the formation of hard tissues of animals. Namely, the basic inorganic building blocks of bones and teeth of mammals are nanodimensional and nanocrystalline calcium orthophosphates (in the form of apatites) of a biological origin. In mammals, tens to hundreds nanocrystals of a biological apatite were found to be combined into self-assembled structures under the control of various bioorganic matrixes. In addition, the structures of both dental enamel and bones could be mimicked by an oriented aggregation of nanosized calcium orthophosphates, determined by the biomolecules. The application and prospective use of nanodimensional and nanocrystalline calcium orthophosphates for a clinical repair of damaged bones and teeth are also known. For example, a greater viability and a better proliferation of various types of cells were detected on smaller crystals of calcium orthophosphates. Thus, the nanodimensional and nanocrystalline forms of calcium orthophosphates have a great potential to revolutionize the field of hard tissue engineering starting from bone repair and augmentation to the controlled drug delivery devices. This paper reviews current state of knowledge and recent developments of this subject starting from the synthesis and characterization to biomedical and clinical applications. More to the point, this review provides possible directions of future research and development.

Deposition of hermetic silver shells onto copper flakes.

PubMed

Njagi, John I; Netzband, Christopher M; Goia, Dan V

2017-02-15

Continuous silver shells were deposited on copper flakes using a two-stage precipitation process. A tightly packed layer of silver nanoparticles was first formed on the surface of the base metal by galvanic displacement. The size of the noble metal particles and their distribution on the substrate were controlled using complexing agents and dispersants. A continuous Ag deposit was subsequently grown by reducing slowly [Ag(NH 3 ) 2 ] + ions with glucose. The final shell thickness was controlled by varying the amount of metal deposited in the second step. The electrical properties of resulting silver coated copper flakes are comparable to those measured for silver flakes of similar size and aspect ratio. By preventing the oxidation of copper cores up to 400°C, the hermetic noble metal shell dramatically extends the temperature range in which Ag/Cu flakes can successfully replace pure silver. Copyright © 2016 Elsevier Inc. All rights reserved.

Dermal exposure potential from textiles that contain silver nanoparticles

PubMed Central

Stefaniak, Aleksandr B; Duling, Mathew G; Lawrence, Robert B; Thomas, Treye A; LeBouf, Ryan F; Wade, Eleanor E; Abbas Virji, M

2014-01-01

Background: Factors that influence exposure to silver particles from the use of textiles are not well understood. Objectives: The aim of this study was to evaluate the influence of product treatment and physiological factors on silver release from two textiles. Methods: Atomic and absorbance spectroscopy, electron microscopy, and dynamic light scattering (DLS) were applied to characterize the chemical and physical properties of the textiles and evaluate silver release in artificial sweat and saliva under varying physiological conditions. One textile had silver incorporated into fiber threads (masterbatch process) and the other had silver nanoparticles coated on fiber surfaces (finishing process). Results: Several complementary and confirmatory analytical techniques (spectroscopy, microscopy, etc.) were required to properly assess silver release. Silver released into artificial sweat or saliva was primarily in ionic form. In a simulated “use” and laundering experiment, the total cumulative amount of silver ion released was greater for the finishing process textile (0.51±0.04%) than the masterbatch process textile (0.21±0.01%); P<0.01. Conclusions: We found that the process (masterbatch vs finishing) used to treat textile fibers was a more influential exposure factor than physiological properties of artificial sweat or saliva. PMID:25000110

Dermal exposure potential from textiles that contain silver nanoparticles.

PubMed

Stefaniak, Aleksandr B; Duling, Mathew G; Lawrence, Robert B; Thomas, Treye A; LeBouf, Ryan F; Wade, Eleanor E; Virji, M Abbas

2014-01-01

Factors that influence exposure to silver particles from the use of textiles are not well understood. The aim of this study was to evaluate the influence of product treatment and physiological factors on silver release from two textiles. Atomic and absorbance spectroscopy, electron microscopy, and dynamic light scattering (DLS) were applied to characterize the chemical and physical properties of the textiles and evaluate silver release in artificial sweat and saliva under varying physiological conditions. One textile had silver incorporated into fiber threads (masterbatch process) and the other had silver nanoparticles coated on fiber surfaces (finishing process). Several complementary and confirmatory analytical techniques (spectroscopy, microscopy, etc.) were required to properly assess silver release. Silver released into artificial sweat or saliva was primarily in ionic form. In a simulated "use" and laundering experiment, the total cumulative amount of silver ion released was greater for the finishing process textile (0·51±0·04%) than the masterbatch process textile (0·21±0·01%); P<0·01. We found that the process (masterbatch vs finishing) used to treat textile fibers was a more influential exposure factor than physiological properties of artificial sweat or saliva.

Nanocrystalline cellulose from coir fiber: preparation, properties, and applications

USDA-ARS?s Scientific Manuscript database

Nanocrystalline cellulose derived from various botanical sources offers unique and potentially useful characteristics. In principle, any cellulosic material can be considered as a potential source of a nanocrystalline material, including crops, crop residues, and agroindustrial wastes. Because of t...

Silver nanoparticle-induced cytotoxicity in rat brain endothelial cell culture.

PubMed

Grosse, Susann; Evje, Lars; Syversen, Tore

2013-02-01

Silver nanoparticles (AgNPs) are among the most widely commercialised engineered nanomaterials, because of their antimicrobial properties. They are already commonly used in medical devices, household products and industry. Concerns have been raised about potential adverse health effects due to increasing dispersion of AgNPs in the environment. The present study examined the cytotoxic effects of spherical, citrate-coated AgNPs (10, 50 and 100 nm) in rat brain endothelial (RBE4) cells and investigated whether the observed effects can be explained by the intrinsic toxicity of the particles or the silver ions released from the particles. The results indicated that exposure of RBE4 cells to AgNPs lead to significant reduction in dye uptake as measured with the Neutral red (NR) assay. The effect was found to be related to particle size, surface area, dose and exposure time. In contrast, silver ions increased NR uptake (ca. 10%) in RBE4 cells after 1h, while a reduction in NR uptake was observed after 24h exposure at high concentrations (20-30 μM). Colony formation, as an indicator of proliferation ability, was completely inhibited by AgNPs at concentrations higher than 1 μg/ml. Silver ions had less effect on the colony formation of RBE4 cells than AgNPs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Green synthesis of silver nanoparticles using Coffea arabica seed extract and its antibacterial activity.

PubMed

Dhand, Vivek; Soumya, L; Bharadwaj, S; Chakra, Shilpa; Bhatt, Deepika; Sreedhar, B

2016-01-01

A novel green source was opted to synthesize silver nanoparticles using dried roasted Coffea arabica seed extract. Bio-reduction of silver was complete when the mixture (AgNO3+extract) changed its color from light to dark brown. UV-vis spectroscopy result showed maximum adsorption at 459 nm, which represents the characteristic surface plasmon resonance of nanosilver. X-ray crystal analysis showed that the silver nanoparticles are highly crystalline and exhibit a cubic, face centered lattice with characteristic (111), (200), (220) and (311) orientations. Particles exhibit spherical and ellipsoidal shaped structures as observed from TEM. Composition analysis obtained from SEM-EDXA confirmed the presence of elemental signature of silver. FTIR results recorded a downward shift of absorption bands between 800-1500 cm(-1) indicting the formation of silver nanoparticles. The mean particle size investigated using DLS was found to be in between 20-30 nm respectively. Anti-bacterial activity of silver nanoparticles on E. coli and S. aureus demonstrated diminished bacterial growth with the development of well-defined inhibition zones. Copyright © 2015 Elsevier B.V. All rights reserved.

Self-organization of silver nanoparticles forming on chemical reduction to give monodisperse spheres

NASA Astrophysics Data System (ADS)

Yakutik, I. M.; Shevchenko, G. P.

2004-09-01

It was found possible to produce monodisperse spherical silver particles using K-Na-tartrate as the reductant for Ag + in the presence of gelatin. It was shown that the silver spheres form in the process of spontaneous self-organization of 10-15 nm-sized primary particles. The conditions making it possible to control the sizes of the monodisperse spheres in the range from 150 nm to 1.5 μm were specified.

Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

PubMed Central

2011-01-01

Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag:Hap nanopowder showed higher inhibition. PMID:22136671

Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

NASA Astrophysics Data System (ADS)

Ciobanu, Carmen Steluta; Massuyeau, Florian; Constantin, Liliana Violeta; Predoi, Daniela

2011-12-01

Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10- x Ag x (PO4)6(OH)2 ( x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp ( x = 0) and Ag:HAp ( x = 0.2). The Ag:Hap nanopowder showed higher inhibition.

Preparation of silver nanoparticles in virgin coconut oil using laser ablation

PubMed Central

Zamiri, Reza; Azmi, B Z; Sadrolhosseini, Amir Reza; Ahangar, Hossein Abbastabar; Zaidan, A W; Mahdi, M A

2011-01-01

Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10−8, 1.6 × 10−8, 2.4 × 10−8, respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method. PMID:21289983

Nanocrystalline Heterojunction Materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2004-02-03

Mesoporous nanocrystalline titanium dioxide heterojunction materials and methods of making the same are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Synthesis of silver-containing calcium aluminate particles and their effects on a MTA-based endodontic sealer.

PubMed

Almeida, Luiza Helena S; Moraes, Rafael R; Morgental, Renata D; Cava, Sérgio S; Rosa, Wellington Luiz O; Rodrigues, Patrícia; Ribeiro, Anderson S; Só, Marcus; Pappen, Fernanda G

2018-05-19

To synthetize calcium aluminate (C3A) and silver-containing C3A particles (C3A+Ag) testing their effects on the properties of a MTA-based endodontic sealer in comparison to an epoxy resin- and a calcium silicate-based sealer. Pure C3A and C3A+Ag particles were synthesized by a chemical method and characterized using XRD to identify crystalline phases. SEM/EDS analysis investigated morphology, particle size, and elemental composition of particles. Setting time, flow, radiopacity, water sorption and solubility of commercial and modified sealers were evaluated according to ISO 6876/2012. The pH and ions release were measured using a pHmeter and a microwave induced plasma optical emission spectrometer. The inhibition of biofilm growth was evaluated by confocal laser scanning microscopy (CLSM). Data were rank transformed and analyzed by ANOVA and Tukey test (P<0.05). The C3A particles showed an irregular grain agglomerated structure with voids and pores. In C3A+Ag particles, Ag modified the material morphology, confirming the deposition of Ag. The physicochemical properties of the modified MTA-based sealer were similar to the commercial material, except for the significant increase in Ca +2 release. However, there was no Ag release. Setting time, flow, radiopacity, water sorption and solubility were adequate for all materials. All the materials showed alkaline pH. Antibiofilm effect was improved in the presence of C3A particles, while the biofilm inhibition was lower in the presence of Ag. The modified sealer presented improved antibiofilm properties and calcium release, without dramatic effects on the other characteristics. It is expected a positive effect in its antimicrobial behavior. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Influence of surface and finite size effects on the structural and magnetic properties of nanocrystalline lanthanum strontium perovskite manganites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Žvátora, Pavel; Veverka, Miroslav; Veverka, Pavel

2013-08-15

Syntheses of nanocrystalline perovskite phases of the general formula La{sub 1−x}Sr{sub x}MnO{sub 3+δ} were carried out employing sol–gel technique followed by thermal treatment at 700–900 °C under oxygen flow. The prepared samples exhibit a rhombohedral structure with space group R3{sup ¯}c in the whole investigated range of composition 0.20≤x≤0.45. The studies were aimed at the chemical composition including oxygen stoichiometry and extrinsic properties, i.e. size of the particles, both influencing the resulting structural and magnetic properties. The oxygen stoichiometry was determined by chemical analysis revealing oxygen excess in most of the studied phases. The excess was particularly high for themore » samples with the smallest crystallites (12–28 nm) while comparative bulk materials showed moderate non-stoichiometry. These differences are tentatively attributed to the surface effects in view of the volume fraction occupied by the upper layer whose atomic composition does not comply with the ideal bulk stoichiometry. - Graphical abstract: Evolution of the particle size with annealing temperature in the nanocrystalline La{sub 0.70}Sr{sub 0.30}MnO{sub 3+δ} phase. Display Omitted - Highlights: • The magnetic behaviour of nanocrystalline La{sub 1−x}Sr{sub x}MnO{sub 3+δ} phases was analyzed on the basis of their crystal structure, chemical composition and size of the particles. • Their Curie temperature and magnetization are markedly affected by finite size and surface effects. • The oxygen excess observed in the La{sub 1−x}Sr{sub x}MnO{sub 3+δ} nanoparticles might be generated by the surface layer with deviated oxygen stoichiometry.« less

Capsaicin-capped silver nanoparticles: its kinetics, characterization and biocompatibility assay

NASA Astrophysics Data System (ADS)

Amruthraj, Nagoth Joseph; Preetam Raj, John Poonga; Lebel, Antoine

2015-04-01

Capsaicin was used as a bio-reductant for the reduction of silver nitrate to form silver nanoparticles. The formation of the silver nanoparticles was initially confirmed by color change and Tyndall effect of light scattering. It was characterized with UV-visible spectroscopy, FTIR and TEM. Hemagglutination (H) test and H-inhibition assay were performed in the presence of AgNPs-capsaicin conjugates. The silver colloid solution after complete reduction turned into pale gray color. The characteristic surface plasmon resonance of silver nanoparticles (SNPs) was observed at 450 nm. Time taken for complete bio-reduction of silver nitrate and capping was found to be 16 hours. The amount of capsaicin required to reduce 20 ml of 1 mM silver nitrate solution was found to be 40 μg approximately. The FTIR results confirmed the capping of capsaicin on the silver metal. The particle size was within the range of 20-30 nm. The hemagglutination and H-inhibition test was negative for all the blood groups. The capsaicin-capped silver nanoparticles were compatible with blood cells in hemagglutination test implying biocompatibility as future therapeutic drug.

Methods for preparation of nanocrystalline rare earth phosphates for lighting applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Comanzo, Holly Ann; Manoharan, Mohan; Martins Loureiro, Sergio Paulo

Disclosed here are methods for the preparation of optionally activated nanocrystalline rare earth phosphates. The optionally activated nanocrystalline rare earth phosphates may be used as one or more of quantum-splitting phosphor, visible-light emitting phosphor, vacuum-UV absorbing phosphor, and UV-emitting phosphor. Also disclosed herein are discharge lamps comprising the optionally activated nanocrystalline rare earth phosphates provided by these methods.

Heterogeneous precipitation of silver nanoparticles on kaolinite plates

NASA Astrophysics Data System (ADS)

Cabal, B.; Torrecillas, R.; Malpartida, F.; Moya, J. S.

2010-11-01

Two different methods to obtain silver nanoparticles supported on kaolin crystals have been performed: the first one followed a thermal reduction and the second one a chemical reduction. In both cases, the silver nanoparticles with two different average particles size (ca.12 and 30 nm) were perfectly isolated and attached to the surface of the kaolin plates. The silver nanoparticles were localized mainly at the edge of the single crystal plates, the hydroxyl groups being the main centres of adsorption. The samples were fully characterized by XRD, UV-vis spectroscopy and TEM. The antimicrobial benefits of the composites were evaluated as antibacterial against common Gram-positive and Gram-negative bacteria, and antifungal activity against yeast. The results indicated a high antimicrobial activity for Escherichia coli JM 110 and Micrococcus luteus, while being inactive against yeast under our experimental conditions. The chemical analysis of Ag in the fermentation broths show that only a small portion of metal (<9 ppm) is released from the kaolin/metakaolin particles. Therefore, the risk of toxicity due to a high concentration of metal in the medium is minimized.

Silver Nanowire Exposure Results in Internalization and Toxicity to Daphnia Magna

PubMed Central

Scanlan, Leona D.; Reed, Robert B.; Loguinov, Alexandre V.; Antczak, Philipp; Tagmount, Abderrahmane; Aloni, Shaul; Nowinski, Daniel Thomas; Luong, Pauline; Tran, Christine; Karunaratne, Nadeeka; Pham, Don; Lin, Xin Xin; Falciani, Francesco; Higgins, Chris P.; Ranville, James F.; Vulpe, Chris D.; Gilbert, Benjamin

2013-01-01

Nanowires (NWs), high-aspect-ratio nanomaterials, are increasingly used in technological materials and consumer products and may have toxicological characteristics distinct from nanoparticles. We carried out a comprehensive evaluation of the physico-chemical stability of four silver nanowires (AgNWs) of two sizes and coatings and their toxicity to Daphnia magna. Inorganic aluminum-doped silica coatings were less effective than organic poly(vinyl pyrrolidone) coatings at preventing silver oxidation or Ag+ release and underwent a significant morphological transformation within one-hour following addition to low ionic strength Daphnia growth media. All AgNWs were highly toxic to D. magna but less toxic than ionic silver. Toxicity varied as a function of AgNW dimension, coating and solution chemistry. Ag+ release in the media could not account for observed AgNW toxicity. Single-particle inductively coupled plasma mass spectrometry (spICPMS) distinguished and quantified dissolved and nanoparticulate silver in microliter-scale volumes of Daphnia magna hemolymph with a limit of detection of approximately 10 ppb. The silver levels within the hemolymph of Daphnia exposed to both Ag+ and AgNW met or exceeded the initial concentration in the growth medium, indicating effective accumulation during filter feeding. Silver-rich particles were the predominant form of silver in hemolymph following exposure to both AgNWs and Ag+. Scanning electron microscopy (SEM) imaging of dried hemolymph found both AgNWs and silver precipitates that were not present in the AgNW stock or the growth medium. Both organic and inorganic coatings on the AgNW were transformed during ingestion or absorption. Pathway, gene ontology and clustering analyses of gene expression response indicated effects of AgNWs distinct from ionic silver on Daphnia magna. PMID:24099093

Nanocrystalline cerium oxide materials for solid fuel cell systems

DOEpatents

Brinkman, Kyle S

2015-05-05

Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

Synthesis and Optical Properties of Silver Bicrystalline Nanowires

NASA Astrophysics Data System (ADS)

Sun, Yugang; Xia, Younan

2002-11-01

This paper describes a solution-phase route to the large-scale synthesis of silver nanowires with diameters in the range of 30-40 nm, and lengths up to ~50 μm. The initial step of this synthesis involved the formation of Pt nanoparticles by reducing PtCl2 with ethylene glycol (EG) refluxed at ~160 °C. These Pt nanoparticles could serve as seeds for the growth of silver (formed by reducing AgNO3 with EG) through heterogeneous nucleation process because their crystal structures and lattice constants matched closely. In the presence of poly(vinyl pyrrolidone) (PVP), the growth of silver could be led to a highly anisotropic mode with formation of uniform nanowires. UV-visible spectroscopy was used to track the growth process of silver nanowires because different silver nanostructures exhibited distinctive surface plasmon resonance peaks at different frequencies. SEM, TEM, XRD, and electron diffraction were used to characterize these silver nanowires, indicating the formation of a highly pure face-centered cubic phase, as well as uniform diameter and bicrystalline structure. The morphology of these silver nanostructures could be varied from particles and rods to long wires by tuning the reaction conditions, including reaction temperature, and the ratio of PVP to silver nitrate. These silver nanowires could be used as sacrificial templates to synthesize gold nanotubes via a template-engaged replacement reaction. The dispersion of gold nanotubes exhibited a strong extinction peak in the red regime, which was around 760 nm.

Antimicrobial activity of silver nanoparticles synthesized using honey and gamma radiation against silver-resistant bacteria from wounds and burns

NASA Astrophysics Data System (ADS)

Hosny, A. M. S.; Kashef, M. T.; Rasmy, S. A.; Aboul-Magd, D. S.; El-Bazza, Z. E.

2017-12-01

Silver nanoparticles (AgNPs) are promising antimicrobial agents for treatment of wounds and burns. We synthesized AgNPs using honey at different pH values or with different gamma irradiation doses. The resulting nanoparticles were characterized by UV-vis spectroscopy, TEM, DLS and FTIR. Their antimicrobial activity, against standard bacterial strains and silver-resistant clinical isolates from infected wounds and burns, was evaluated in vitro through determination of their minimum inhibitory concentration (MIC). AgNPs prepared using 30 g of honey exposed to 5 kGy gamma radiation had the best physical characters regarding stability and uniformity of particle size and shape. They recorded the lowest MIC values against both the standard and silver-resistant isolates. In conclusion, honey and gamma radiation can be used in synthesis of highly stable pure AgNPs, without affecting the physico-chemical and antimicrobial activity of honey. This offered an advantage in terms of inhibition of silver-resistant bacteria isolates.

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

DOE PAGES

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.; ...

2016-03-11

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Experiments on the contact angle of n-propanol on differently prepared silver substrates at various temperatures and implications for the properties of silver nanoparticles

NASA Astrophysics Data System (ADS)

Pinterich, T.; Winkler, P. M.; Vrtala, A. E.; Wagner, P. E.

2011-08-01

In this paper we present the results of contact angle measurements between n-propanol and silver substrates in the temperature range from -10 °C to 30 °C. The interest in a potential temperature dependence of contact angles originates from recent experiments by S. Schobesberger et al. (Schobesberger S., Strange temperature dependence observed for heterogeneous nucleation of n-propanol vapor on NaCl particles. Master's thesis, University of Vienna, 2008; Schobesberger S. et al., Experiments on the temperature dependence of heterogeneous nucleation on NaCl and Ag particles. In preparation.) investigating the temperature dependence for heterogeneous nucleation of n-propanol vapour on NaCl and on silver particles. We determined dynamic advancing θ a and receding θ r angles on variously prepared silver probes. The Dynamic Wilhelmy method (Wilhelmy L., Über die Abhängigkeit der Capillaritäts-Constanten des Alkohols von Substanz und Gestalt des benetzten festen Körpers. Ann. Phys. Chem., 199:177-217, 1863) was applied using a Krüss K12 Tensiometer, with a refrigerated double-walled glass top. With respect to its potential influence on heterogeneous nucleation mainly the advancing angle is of interest. The uniform probe geometry required was achieved by accurate cutting and by multiple polishing stages up to the accomplishment of a 0.04 μm grain size. The original probes consist of 925 sterling silver including a 7.5% copper content. Additional coating with silver pro Analysi (p.A.) was applied making use of pure silver powder evaporation process via Physical Vapour Deposition (PVD). Results show that a surface contamination by copper cannot be neglected for the specification of contact angles. It turned out that additional PVD coatings not only change the values of θa but also their temperature dependence. With increasing the number of coatings of a plate the contact angle decreases and its temperature dependence inverts. Since the contact angle hysteresis �

A re-assessment of the safety of silver in household water treatment: rapid systematic review of mammalian in vivo genotoxicity studies.

PubMed

Fewtrell, Lorna; Majuru, Batsirai; Hunter, Paul R

2017-06-20

Despite poor evidence of their effectiveness, colloidal silver and silver nanoparticles are increasingly being promoted for treating potentially contaminated drinking water in low income countries. Recently, however, concerns have been raised about the possible genotoxicity of particulate silver. The goal of this paper was to review the published mammalian in vivo genotoxicity studies using silver micro and nanoparticles. SCOPUS and Medline were searched using the following search string: ("DNA damage" OR genotox* OR Cytotox* OR Embryotox*) AND (silver OR AgNP). Included papers were any mammalian in vivo experimental studies investigating genotoxicity of silver particles. Studies were quality assessed using the ToxRTool. 16 relevant papers were identified. There were substantial variations in study design including the size of silver particles, animal species, target organs, silver dose, route of administration and the method used to detect genotoxicity. Thus, it was not possible to produce a definitive pooled result. Nevertheless, most studies showed evidence of genotoxicity unless using very low doses. We also identified one human study reporting evidence of "severe DNA damage" in silver jewellery workers occupationally exposed to silver particles. With the available evidence it is not possible to be definitive about risks to human health from oral exposure to silver particulates. However, the balance of evidence suggests that there should be concerns especially when considering the evidence from jewellery workers. There is an urgent need to determine whether people exposed to particulate silver as part of drinking water treatment have evidence of DNA damage.

Ga2O3 and GaN nanocrystalline film: reverse micelle assisted solvothermal synthesis and characterization.

PubMed

Sinha, Godhuli; Ganguli, Dibyendu; Chaudhuri, Subhadra

2008-03-01

Gallium oxide (beta-Ga2O3) nanoparticles were successfully deposited on quartz glass substrates using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-hexane/ethylene glycol monomethyl ether (EGME) reverse micelle-mediated solvothermal process with different omega values. The mean diameter of Ga2O3 particles was approximately 2-3 nm and found to be approximately independent of omega values of the reverse micelles. However, when the Ga2O3 nanocrystalline films were nitrided at 900 degrees C under flowing NH3 atmosphere for 1 h, the mean diameter of the resulted gallium nitride (wurtzite-GaN) nanoparticles varied from 3-9 nm. Both nanocrystalline films of Ga2O3 and GaN were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence in order to study their chemical and physical properties explicitly.

Green Synthesis of Silver Nanoparticles Using an Aqueous Extract of Monotheca buxifolia (Flac.) Dcne

NASA Astrophysics Data System (ADS)

Anwar, Natasha; Khan, Abbas; Shah, Mohib; Anwar, Saad

2018-01-01

This study deals with the synthesis and physicochemical investigation of silver nanoparticles using an aqueous extract of Monotheca buxifolia (Flac.). On the treatment of aqueous solution of silver nitrate with the plant extract, silver nanoparticles were rapidly fabricated. The synthesized particles were characterized by using UV-visible spectrophotometry (UV), Fourier transform infrared spectroscopy (FTIR), Energy dispersive X-ray (EDX) and Scanning electron microscopy (SEM). The formation of AgNPs was confirmed by noting the change in colour through visual observations as well as via UV-Vis spectroscopy. UV-Vis spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 440 nm. FTIR was used to identify the chemical composition of silver nanoparticles and Ag-capped plant extract. The presence of elemental silver was also confirmed through EDX analysis. The SEM analysis of the silver nanoparticles showed that they have a uniform spherical shape with an average size in the range of 40-78 nm. This green system showed better capping and stabilizing agent for the fine particles. Further, in vitro the antioxidant activity of Monotheca buxifolia (Flac.) and Ag-capped with the plant was also evaluated using FeCl3/K3Fe (CN)6 essay.

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

NASA Astrophysics Data System (ADS)

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

2011-11-01

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.

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

PubMed

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

2011-11-01

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. Copyright © 2011 Elsevier B.V. All rights reserved.

Development of silica-encapsulated silver nanoparticles as contrast agents intended for dual-energy mammography.

PubMed

Karunamuni, Roshan; Naha, Pratap C; Lau, Kristen C; Al-Zaki, Ajlan; Popov, Anatoliy V; Delikatny, Edward J; Tsourkas, Andrew; Cormode, David P; Maidment, Andrew D A

2016-09-01

Dual-energy (DE) mammography has recently entered the clinic. Previous theoretical and phantom studies demonstrated that silver provides greater contrast than iodine for this technique. Our objective was to characterize and evaluate in vivo a prototype silver contrast agent ultimately intended for DE mammography. The prototype silver contrast agent was synthesized using a three-step process: synthesis of a silver core, silica encapsulation and PEG coating. The nanoparticles were then injected into mice to determine their accumulation in various organs, blood half-life and dual-energy contrast. All animal procedures were approved by the institutional animal care and use committee. The final diameter of the nanoparticles was measured to be 102 (±9) nm. The particles were removed from the vascular circulation with a half-life of 15 min, and accumulated in macrophage-rich organs such as the liver, spleen and lymph nodes. Dual-energy subtraction techniques increased the signal difference-to-noise ratio of the particles by as much as a factor of 15.2 compared to the single-energy images. These nanoparticles produced no adverse effects in mice. Silver nanoparticles are an effective contrast agent for dual-energy x-ray imaging. With further design improvements, silver nanoparticles may prove valuable in breast cancer screening and diagnosis. • Silver has potential as a contrast agent for DE mammography. • Silica-coated silver nanoparticles are biocompatible and suited for in vivo use. • Silver nanoparticles produce strong contrast in vivo using DE mammography imaging systems.

Preparation and application of silver nanopaste as thermal interface materials

NASA Astrophysics Data System (ADS)

Zou, Lianfeng

The power densities in electronic devices have increased dramatically; heat dissipation has become a major challenge in high performance electronics applications. We have investigated a new type of resin-free hybrid silver nanopastes, which contain silver micro-flakes with particle sizes of 1 - 10 um and silver nanoparticles with diameters of 3 - 8 nm. The assemble temperature can be as low as 150oC due to the low sintering temperature of silver nanoparticles. The fused silver micro-and nanoparticles in TIM form continuous metallic networks, resulting in good thermal, electrical and mechanical bonding. The steady-state thermal gradient measurement show the bulk thermal conductivity between 20W/ (m*K) and 100 W/ (m*K), which is higher than commercial product in the market. The application specific performance of the nanopaste has been using LED lamp on heat sinks as model test vehicle.

Comparison of nanosilver and ionic silver toxicity in Daphnia magna and Pimephales promelas

EPA Science Inventory

This work evaluates the relative contribution of soluble (Ag+) silver and and nano-scale silver particles (n-Ag) and thus addresses an important issue relative to potential ecological risk of n-Ag and of other partially-soluble metal nanoparticles. We used acute to chronic (based...

Adsorption of CGA on colloidal silver particles: DFT and SERS study

NASA Astrophysics Data System (ADS)

Biswas, Nandita; Kapoor, Sudhir; Mahal, Harbir S.; Mukherjee, Tulsi

2007-08-01

Raman and surface-enhanced Raman scattering (SERS) of chlorogenic acid (CGA) have been investigated. CGA is an important plant metabolite with anti-viral and anti-bacterial properties and thus, it is useful to study its surface adsorption characteristics. The experimental Raman data is supported with DFT calculations using B3LYP functional with 6-31G ∗ and LANL2DZ basis set. This is the first report on the vibrational analysis of CGA and its silver complex. From the SERS spectra as well as theoretical calculations, it has been inferred that the molecule is chemisorbed to the silver surface through the oxygen atoms of the carboxylate group.

Bio-synthesis and antimicrobial activity of silver nanoparticles using anaerobically digested parthenium slurry.

PubMed

Adur, Alaknanda J; Nandini, N; Shilpashree Mayachar, K; Ramya, R; Srinatha, N

2018-06-01

Silver nanoparticles were prepared through eco-friendly, cost effective, bio-mediated technique using anaerobically digested Parthenium hysterophorous digested slurry (PDS) for the first time. The synthesized nanoparticles were characterized through different techniques such as UV-Vis spectrophotometer for optical properties; X-ray diffractometer (XRD), high resolution transmission electron spectroscopy (HR-TEM) and Fourier Transform Infra Red (FTIR) Spectroscopy for structural property investigations. It was observed that the prepared silver nanoparticles were crystallized in face centered cubic crystal structure with an average particle size of 19 nm as confirmed from XRD. Also HR-TEM studies reveal the formation of nano-sized silver particles with face centered cubic nano structure. In addition, absorption spectra exhibit Surface Plasmon Resonance (SPR) which suggests the formation of silver nanoparticles. FTIR results show the presence of different characteristic functional groups and their stretching / bending vibrations in turn responsible for the bioreduction of silver ions in Parthenium digested slurry. Further investigations on antimicrobial activity were done by subjecting the synthesized silver nanoparticles on E-coli and Pseudomonas as marker organisms for the group of gram negative bacteria by well plate method on enrichment media. The result obtained shows a clear zone of inhibition confirming the antibacterial activity. Overall, the investigated results confirm the biosynthesized silver nanoparticles are potential candidates for antimicrobial activity applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis and Study of Silver Nanoparticles

ERIC Educational Resources Information Center

Soloman, Sally D.; Bahadory, Mozghan; Jeyarajasingam, Aravindan V.; Rutkowsky, Susan A.; Boritz, Charles; Mulfinger, Lorraine

2007-01-01

A laboratory experiment was conducted in which the students synthesized yellow colloidal silver, estimate particle size using visible spectroscopy and studied aggregation effects. The students were thus introduced to nanotechnology along with other topics such as redox chemistry, limiting and excess reactants, spectroscopy and atomic size.

Sunlight-assisted synthesis of colloidal silver nanoparticles using chitosan as reducing agent

NASA Astrophysics Data System (ADS)

Susilowati, E.; Maryani; Ashadi

2018-04-01

The present study we explore an environmentally friendly colloidal silver nanoparticles preparation using chitosan as reducing agent and stabilizer. It develops a new strategy on preparation of silver nanoparticles through the gel phase using sodium hydroxide (NaOH) as accelerator reagent. Sunlight irradiation was employed to assisted reducing process of silver ions to silver nanoparticles. Localized surface plasmon resonance (LSPR) phenomenon of silver nanoparticles was investigated using UV-Vis spectrophotometer. The shape and size of silver particles were analyzed using TEM. The formation of silver nanoparticles was confirmed by the appearance of LSPR absorption peak at 396.0–412.0 nm. The absorption peak of LSPR were affected by NaOH amount, time of sulight irradiation and concentration of AgNO3. The produced silver nanoparticles were spherical with dominant size range of 5 to 8 nm as shown by TEM images. All colloidals were stable without any aggregation for 30 days after preparation.

Synthesis of dextrin-stabilized colloidal silver nanoparticles and their application as modifiers of cement mortar.

PubMed

Konował, Emilia; Sybis, Marta; Modrzejewska-Sikorska, Anna; Milczarek, Grzegorz

2017-11-01

Various commercial dextrins were used as reducing and stabilizing agents for a novel one-step synthesis of silver nanoparticles from ammonia complexes of silver ions. As a result, stable colloids of silver were formed during the reaction with the particle size being the function of the dextrin type. The obtained colloids were characterized by UV-vis spectrophotometry, size distribution (using Non-Invasive Backscatter optics) and transmission electron microscopy (TEM). The achieved results clearly indicate the possibility of low-cost production of large quantities of colloidal silver nanoparticles using materials derived from renewable sources. The resulting silver colloids can be used for different purposes, e.g. as bactericidal agents. Combination of the aforementioned properties of nanosilver particles with plasticizing properties of dextrin enables to obtain cement mortars with increased workability and enhanced compressive strength. Moreover, the obtained material is also characterized by increased immunity to adverse impact of microorganisms. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis of Silver nanoparticles (AgNPs) with Antibacterial Activity

NASA Astrophysics Data System (ADS)

Campillo Gloria, E.; Ederley, Vélez; Gladis, Morales; César, Hincapié; Jaime, Osorio; Oscar, Arnache; Uribe José, Ignacio; Franklin, Jaramillo

2017-06-01

The synthesis of nanomaterials is currently one of the most active in nanoscience branches; especially those help improve the human quality life. Silver nanoparticles (AgNPs) are an example of this as it is known to have inhibitory and bactericidal effects. In this work, we report the synthesis of silver nanoparticles by chemical reduction method of silver nitrate (AgNO3) from aqueous solution, using a mix of polivinyl pyrrolidone (PVP) - Aloe Vera as reducing agent and for stabilization and control of particle size. Silver nanoparticles obtained were characterized by Scanning Electron Microscopy (SEM), UV-visible spectroscopy and measurements using Zetasizer Nano ZS were applied to size estimation. The existence of surface plasmon resonance peak at λmax ~ 420 nm is evidence of silver nanoparticles formation. It was possible to standardize an appropriate protocol for the evaluation of bactericidal activity of the nanoparticles, for mesophilic microorganisms. Bactericidal activity above 90% against these kinds of bacteria was demonstrated.

Green synthesis of silver nanoparticle using Bambusa arundinacea leaves

NASA Astrophysics Data System (ADS)

Kataria, Bharat; Shyam, Vasvani; Kaushik, Babiya; Vasoya, Jaydeep; Joseph, Joyce; Savaliya, Chirag; Kumar, Sumit; Parikh, Sachin P.; Thakar, C. M.; Pandya, D. D.; Ravalia, A. B.; Markna, J. H.; Shah, N. A.

2017-05-01

The synthesis of nanoparticles using ecofriendly way is an interesting area in advance nanotechnology. Silver (Ag) nanoparticles are usually synthesized by chemicals route, which are quite flammable and toxic in nature. This study deals with a biosynthesis process (environment friendly) of silver nanoparticles using Bambusa arundinacea leaves for its antibacterial activity. The formation and characterization of AgNPs was confirmed by UV-Vis spectroscopy. Silver nanoparticles were successfully synthesized from AgNO3 through a simple green route using the latex of Bambusa arundinacea leaves as reducing as well as capping agent. Scanning Electron Microscopy (SEM) study indicates the formation of grains (particles) with different size and shape.

Field-assisted synthesis of SERS-active silver nanoparticles using conducting polymers

NASA Astrophysics Data System (ADS)

Xu, Ping; Jeon, Sea-Ho; Mack, Nathan H.; Doorn, Stephen K.; Williams, Darrick J.; Han, Xijiang; Wang, Hsing-Lin

2010-08-01

A gradient of novel silver nanostructures with widely varying sizes and morphologies is fabricated on a single conducting polyaniline-graphite (P-G) membrane with the assistance of an external electric field. It is believed that the formation of such a silver gradient is a synergetic consequence of the generation of a silver ion concentration gradient along with an electrokinetic flow of silver ions in the field-assisted model, which greatly influences the nucleation and growth mechanism of Ag particles on the P-G membrane. The produced silver dendrites, flowers and microspheres, with sharp edges, intersections and bifurcations, all present strong surface enhanced Raman spectroscopy (SERS) responses toward an organic target molecule, mercaptobenzoic acid (MBA). This facile field-assisted synthesis of Ag nanoparticles via chemical reduction presents an alternative approach to nanomaterial fabrication, which can yield a wide range of unique structures with enhanced optical properties that were previously inaccessible by other synthetic routes.A gradient of novel silver nanostructures with widely varying sizes and morphologies is fabricated on a single conducting polyaniline-graphite (P-G) membrane with the assistance of an external electric field. It is believed that the formation of such a silver gradient is a synergetic consequence of the generation of a silver ion concentration gradient along with an electrokinetic flow of silver ions in the field-assisted model, which greatly influences the nucleation and growth mechanism of Ag particles on the P-G membrane. The produced silver dendrites, flowers and microspheres, with sharp edges, intersections and bifurcations, all present strong surface enhanced Raman spectroscopy (SERS) responses toward an organic target molecule, mercaptobenzoic acid (MBA). This facile field-assisted synthesis of Ag nanoparticles via chemical reduction presents an alternative approach to nanomaterial fabrication, which can yield a wide range

Optimization of silver-dielectric-silver nanoshell for sensing applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirzaditabar, Farzad; Saliminasab, Maryam

2013-08-15

In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivitymore » of silver-dielectric-silver nanoshell.« less

Continuous 3-day exposure assessment of workplace manufacturing silver nanoparticles

NASA Astrophysics Data System (ADS)

Lee, Ji Hyun; Ahn, Kangho; Kim, Sun Man; Jeon, Ki Soo; Lee, Jong Seong; Yu, Il Je

2012-09-01

With the increased production and widespread use of nanomaterials, human and environmental exposure to nanomaterials is inevitably increasing. Therefore, this study monitored the possible nanoparticle exposure at a workplace that manufactures silver nanoparticles. To estimate the potential exposure of workers, personal sampling, area monitoring, and real-time monitoring were conducted over 3 days using a scanning mobility particle sizer and dust monitor at a workplace where the workers handle nanomaterials. The area sampling concentrations obtained from the injection room showed the highest concentration, ranging from 0.00501 to 0.28873 mg/m3. However, apart from the injection room, none of the area samplings obtained from other locations showed a concentration higher than 0.0013 mg/m3. Meanwhile, the personal sampling concentrations ranged from 0.00004 to 0.00243 mg/m3 over the 3 days of sampling, which was much lower than the silver TLV. The particle number concentrations at the silver nanoparticle manufacturing workplace were 911,170 (1st day), 1,631,230 (2nd day), and 1,265,024 (3rd day) particles/cm3 with a size range of 15-710.5 nm during the operation of the reactor, while the concentration decreased to 877,364.9 (1st day), 492,732 (2nd day), and 344,343 (3rd day) particles/cm3 when the reactor was stopped.

Some aspects of pulsed laser deposition of Si nanocrystalline films

NASA Astrophysics Data System (ADS)

Polyakov, B.; Petruhins, A.; Butikova, J.; Kuzmin, A.; Tale, I.

2009-11-01

Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed. in here

Electrodeposition of Nanocrystalline Co-P Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2009-09-02

Electrodeposition  of Nanocrystalline Co‐P  Coatings as a Hard Chrome Alternative Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden...AND SUBTITLE Electrodeposition of Nanocrystalline Co‐P Coatings as a Hard Chrome Alternative 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Defense Conference – 2 September 2009 Conventional  Electrodeposits Polycrystalline (10‐100 µm) Electrodeposited Nanocrystalline Materials Pulsed

Structural, optical and magnetic behaviour of nanocrystalline Volborthite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arvind, Hemant K., E-mail: hemantarvind@gmail.com; Kumar, Sudhish, E-mail: skmlsu@gmail.com; Kalal, Sangeeta

2016-05-06

Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu{sub 3}V{sub 2} (OH){sub 2}O{sub 7}.2H{sub 2}O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be E{sub g}= ∼2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity andmore » retentivity at room temperature.« less

Detection of silver nanoparticles in cells by flow cytometry using light scatter and far-red fluorescence.

PubMed

Zucker, R M; Daniel, K M; Massaro, E J; Karafas, S J; Degn, L L; Boyes, W K

2013-10-01

The cellular uptake of different sized silver nanoparticles (AgNP) (10, 50, and 75 nm) coated with polyvinylpyrrolidone (PVP) or citrate on a human derived retinal pigment epithelial cell line (ARPE-19) was detected by flow cytometry following 24-h incubation of the cells with AgNP. A dose dependent increase of side scatter and far red fluorescence was observed with both PVP and citrate-coated 50 nm or 75 nm silver particles. Using five different flow cytometers, a far red fluorescence signal in the 700-800 nm range increased as much as 100 times background as a ratio comparing the intensity measurements of treated sample and controls. The citrate-coated silver nanoparticles (AgNP) revealed slightly more side scatter and far red fluorescence than did the PVP coated silver nanoparticles. This increased far red fluorescence signal was observed with 50 and 75 nm particles, but not with 10 nm particles. Morphological evaluation by dark field microscopy showed silver particles (50 and 75 nm) clumped and concentrated around the nucleus. One possible hypothesis to explain the emission of far red fluorescence from cells incubated with silver nanoparticles is that the silver nanoparticles inside cells agglomerate into small nano clusters that form surface plasmon resonance which interacts with laser light to emit a strong far red fluorescence signal. The results demonstrate that two different parameters (side scatter and far red fluorescence) on standard flow cytometers can be used to detect and observe metallic nanoparticles inside cells. The strength of the far red fluorescence suggests that it may be particularly useful for applications that require high sensitivity. © Published 2013 Wiley-Periodicals, Inc. Published 2013 Wiley‐Periodicals, Inc. This article is a US government work and, as such, is in the public domain in the United States of America.

TOPO-capped silver selenide nanoparticles and their incorporation into polymer nanofibers using electrospinning technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

More, D.S.; Moloto, M.J., E-mail: makwenam@vut.ac.za; Moloto, N.

Highlights: • Ag{sub 2}Se nanoparticles produced spherical particles with sizes 12 nm (180 °C) and 27 nm (200 °C). • Higher temperature produced increased particle size (∼75 nm) and changed in shape. • Ag{sub 2}Se nanoparticles (0.2–0.6%) added into PVP (35–45%) to yield reduced fiber beading. • Polymer nanofibers electrospun at 11–20 kV produced fiber diameters of 425–461 nm. • Optical properties in the fibers were observed due to the Ag{sub 2}Se nanoparticles loaded. - Abstract: Electrospinning is the most common technique for fabricating polymer fibers as well as nanoparticles embedded polymer fibers. Silver selenide nanoparticles were synthesized using tri-n-octylphosphinemore » (TOP) as solvent and tri-n-octylphosphine oxide (TOPO) as capping environment. Silver selenide was prepared by reacting silver nitrate and selenium with tri-n-octylphosphine (TOP) to form TOP–Ag and TOP–Se solutions. Both absorption and emission spectra signify the formation of nanoparticles as well as the TEM which revealed spherical particles with an average particle size of 22 nm. The polymer, PVP used was prepared at concentrations ranging from (35 to 45 wt%) and the TOPO-capped silver selenide nanoparticles (0.2 and 0.6 wt%) were incorporated into them and electrospun by varying the voltage from 11 to 20 kV. The SEM images of the Ag{sub 2}Se/PVP composite fibers revealed the fibers of diameters with average values of 425 and 461 nm. The X-ray diffraction results show peaks which were identified due to α-Ag{sub 2}Se body centered cubic compound. The sharp peak observed for all the samples at 2θ = 44.5 suggest the presence of Ag in the face centered cubic which can be attributed to higher concentration of silver nitrate used with molar ratio of selenium to silver and the abundance of silver in the silver selenide crystal. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA) and ultraviolet–visible spectroscopy were used to

In Vitro Parallel Evaluation of Antibacterial Activity and Cytotoxicity of Commercially Available Silver-Containing Wound Dressings.

PubMed

Yunoki, Shunji; Kohta, Masushi; Ohyabu, Yoshimi; Iwasaki, Tetsuji

2015-01-01

This study evaluated the in vitro antibacterial activity and cytotoxicity of various commercially available silver-containing dressings (Ag dressing). Biohesive Ag (hydrocolloid, silver sulfadiazine), Aquacel® Ag (nonwoven fabric, ionic silver [Ag]), Algisite™ Ag (nonwoven fabric, Ag), Mepilex® Ag (foam, silver sulfate), and PolyMem® Ag (foam, nanocrystalline silver) were tested for characteristics of Ag release, antibacterial activity, and cytotoxicity. The release of Ag was investigated in cell culture medium at immersion periods of 6, 24, and 48 hours. The antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa were accessed by a disc diffusion test. The cytotoxicity was evaluated using V79 cells, by an extraction method. The cytotoxicity was not a monotonic function of the antibacterial activity among the Ag dressings and could not be simply explained by Ag-release properties. Biohesive Ag was regarded as a slow-release Ag dressing, showing the lowest cytotoxicity, while the antibacterial activity was classified as "strong" or "significant" against the two species of bacteria. Aquacel Ag and Algisite Ag showed higher antibacterial activity and cytotoxic effects, which were supported by the higher Ag release. Mepilex Ag showed the highest release of Ag, and the cytotoxicity was the highest among the Ag dressings. However, the antibacterial activity was classified as "significant" or "no activity" for P. aeruginosa and S. aureus, respectively. PolyMem Ag showed the lowest Ag release, and the antibacterial activity classified as "significant" or "no activity" for S. aureus and P. aeruginosa, respectively, whereas the cytotoxicity was similar to those of Aquacel Ag and Algisite Ag. The efficacy and adverse effects of the Ag dressings revealed differences that should be considered by clinicians during wound management.

Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds.

PubMed

Dharmshaktu, Ganesh Singh; Singhal, Aanshu; Pangtey, Tanuja

2016-01-01

A good dressing is mandatory to an uncomplicated wound healing, especially when foreign particles contaminate the wound. Various forms of dressing preparations are available for use and differ in chemical composition and efficacy. Silver has been a known agent with good antimicrobial and healing properties and recent times has seen an upsurge in various silver-based dressing supplements. We describe our report of use and efficacy of a silver nanoparticle- based gel dressing in the healing of multiple superficial firearm pellet wounds.

Microstructural studies of nanocrystalline α-alumina powder produced from Al13-cluster

NASA Astrophysics Data System (ADS)

Harun Al Rashid Megat Ahmad, Megat; Aziz Mohamed, Abdul; Ibrahim, Azmi; Seman Mahmood, Che; Giri Rachman Putra, Edy; Jamro, Rafhayudi; Kasim, Razali; Rawi Muhammad Zin, Muhammad

2007-12-01

Nanocrystalline alumina powder was produced from calcinations of Al13-oxalate precipitates at 1100 °C. A nearly normal distribution of agglomerated alumina powder was obtained with an average particle size of about 1 μm. XRD measurement confirmed that the alumina produced was of high purity and crystalline α-phase. Microstructural features of both the precipitates and alumina obtained were studied using the small angle neutron scattering (SANS) technique. SANS examinations show the formation of microstructures in the alumina powder of mass fractals type with dimension of ˜2.8 indicative of low intra-granular porosity.

Microbial Biosynthesis of Silver Nanoparticles in Different Culture Media.

PubMed

Luo, Ke; Jung, Samuel; Park, Kyu-Hwan; Kim, Young-Rok

2018-01-31

Microbial biosynthesis of metal nanoparticles has been extensively studied for the applications in biomedical sciences and engineering. However, the mechanism for their synthesis through microorganism is not completely understood. In this study, several culture media were investigated for their roles in the microbial biosynthesis of silver nanoparticles (AgNPs). The size and morphology of the synthesized AgNPs were analyzed by UV-vis spectroscopy, Fourier-transform-infrared (FT-IR), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The results demonstrated that nutrient broth (NB) and Mueller-Hinton broth (MHB) among tested media effectively reduced silver ions to form AgNPs with different particle size and shape. Although the involved microorganism enhanced the reduction of silver ions, the size and shape of the particles were shown to mainly depend on the culture media. Our findings suggest that the growth media of bacterial culture play an important role in the synthesis of metallic nanoparticles with regard to their size and shape. We believe our findings would provide useful information for further exploration of microbial biosynthesis of AgNPs and their biomedical applications.

A facile sol-gel synthesis of impurity-free nanocrystalline titania.

PubMed

Vinogradov, Alexandr V; Ermakova, Al'ena V; Butman, Mikhail F; Hey-Hawkins, Evamarie; Vinogradov, Vladimir V

2014-06-14

This paper reports an original technique that provides a highly pure crystalline sol of titania with controllable particle size by ultrasonic activation of the hydrolysis products of titanium isopropoxide in an aqueous medium at a near-neutral pH, which is potentially promising in impurity-sensitive electronics and biochemical engineering. Optimal conditions (H2O/TIP ratio, sonication time, etc.) for preparation of stable nanocrystalline titania sol were adopted. A new mechanism of regulation of aggregation and polycondensation under ultrasonic irradiation is proposed. Entrapment of human serum albumin (HSA) in the formed porous titania matrix results in high thermal stability of the protein dopants: the denaturation temperature of HSA is shifted by 31 °C.

The effect of silver nanoparticles on composite shear bond strength to dentin with different adhesion protocols.

PubMed

Fatemeh, Koohpeima; Mohammad Javad, Mokhtari; Samaneh, Khalafi

2017-01-01

The purpose of this study was to investigate the effect of silver nanoparticles on composite shear bond strength using one etch and rinse and one self-etch adhesive systems. Silver nanoparticles were prepared. Transmission electron microscope and X-ray diffraction were used to characterize the structure of the particles. Nanoparticles were applied on exposed dentin and then different adhesives and composites were applied. All samples were tested by universal testing machine and shear bond strength was assesed. Particles with average diameter of about 20 nm and spherical shape were found. Moreover, it was shown that pretreatment by silver nanoparticles enhanced shear bond strength in both etch and rinse, and in self-etch adhesive systems (p≤0.05). Considering the positive antibacterial effects of silver nanoparticles, using them is recommended in restorative dentistry. It seems that silver nanoparticles could have positive effects on bond strength of both etch-and-rinse and self-etch adhesive systems. The best results of silver nanoparticles have been achieved with Adper Single Bond and before acid etching.

Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles

PubMed Central

Singh, Priyanka; Kim, Yeon Ju; Singh, Hina; Wang, Chao; Hwang, Kyu Hyon; Farh, Mohamed El-Agamy; Yang, Deok Chun

2015-01-01

In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antmicrobial efficacy of well-known commercial antibiotics. PMID:25848272

Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles.

PubMed

Singh, Priyanka; Kim, Yeon Ju; Singh, Hina; Wang, Chao; Hwang, Kyu Hyon; Farh, Mohamed El-Agamy; Yang, Deok Chun

2015-01-01

In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antimicrobial efficacy of well-known commercial antibiotics.

Efficient silver modification of TiO2 nanotubes with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Huang, Jing; Ding, Lei; Xi, Yaoning; Shi, Liang; Su, Ge; Gao, Rongjie; Wang, Wei; Dong, Bohua; Cao, Lixin

2018-06-01

In this paper, Ag(CH3NH2)2+, Ag(NH3)2+ and Ag+ with different radii have been used as silver sources to find out the distribution of Ag ions on the H-TNT surface, which is critical to the final performance. The influence of this distribution on visible photocatalytic activity is further studied. The results indicate that, when Ag+ used as silver source with low concentration, these small sized silver ions mainly distribute on interlayer spacing of H-TNT. After heat-treatment and photo-reduction, the generated silver nanoparticles uniformly embed in the anatase TiO2 nanotube walls, and bring large interfacial area between Ag particles and TiO2 nanotubes. The separation effect of photogenerated electron-hole pair in TiO2 is enhanced by Ag particles, and achieves the best at 0.15 g/L, much higher than P25, TiO2/0, Ag-N@TiO2 and Ag-C-N@TiO2. This paper provides new ideas for the modification of TiO2 nanotubes.

Nanocrystalline ZnO as a Visible Active Photocatalyst for the Degradation of Benzene-1,4-diol

NASA Astrophysics Data System (ADS)

Ramachandran, Saranya; Sivasamy, A.

We have synthesized nanocrystalline ZnO by a simple precipitation method. The prepared ZnO was found to be highly phase pure and nanocrystalline hexagonal wurtzite structure. UV-Visible-DRS spectroscopy showed the material to have bandgap energy of 3.22eV. HR-SEM image revealed the material to be made up of distinct hexagonal particles with a highly porous surface. AFM analysis was employed to confirm the high surface roughness and porosity of the material. The photocatalytic activity of the prepared ZnO was evaluated by the degradation of benzene-1,4-diol (hydroquinone), under visible light irradiation. Preliminary experiments showed the catalyst to be effective at neutral pH with an optimum catalyst dosage of 4g/L. Kinetic studies showed the degradation reaction to follow pseudo-first-order kinetics. In the presence of commonly used industrial electrolytes, the catalyst exhibited a decrease in efficiency. Reusability studies showed the catalytic efficiency of ZnO to diminish marginally after the third cycle of reuse.

Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Saber, Mostafa

Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal stability of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal stability. Kinetic and thermodynamic stabilization are the two basic mechanisms with which stability of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal stability of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal stability of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size stabilization was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal stabilization. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The analysis of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha → gamma phase transformation in Fe-Cr-Zr system does not influence the grain size stabilization. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 °C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha → gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth

Fabrication of a silver particle-integrated silicone polymer-covered metal stent against sludge and biofilm formation and stent-induced tissue inflammation

PubMed Central

Lee, Tae Hoon; Jang, Bong Seok; Jung, Min Kyo; Pack, Chan Gi; Choi, Jun-Ho; Park, Do Hyun

2016-01-01

To reduce tissue or tumor ingrowth, covered self-expandable metal stents (SEMSs) have been developed. The effectiveness of covered SEMSs may be attenuated by sludge or stone formation or by stent clogging due to the formation of biofilm on the covering membrane. In this study, we tested the hypothesis that a silicone membrane containing silver particles (Ag-P) would prevent sludge and biofilm formation on the covered SEMS. In vitro, the Ag-P-integrated silicone polymer-covered membrane exhibited sustained antibacterial activity, and there was no definite release of silver ions from the Ag-P-integrated silicone polymer membrane at any time point. Using a porcine stent model, in vivo analysis demonstrated that the Ag-P-integrated silicone polymer-covered SEMS reduced the thickness of the biofilm and the quantity of sludge formed, compared with a conventional silicone-covered SEMS. In vivo, the release of silver ions from an Ag-P-integrated silicone polymer-covered SEMS was not detected in porcine serum. The Ag-P-integrated silicone polymer-covered SEMS also resulted in significantly less stent-related bile duct and subepithelium tissue inflammation than a conventional silicone polymer-covered SEMS. Therefore, the Ag-P-integrated silicone polymer-covered SEMS reduced sludge and biofilm formation and stent-induced pathological changes in tissue. This novel SEMS may prolong the stent patency in clinical application. PMID:27739486

Fabrication of a silver particle-integrated silicone polymer-covered metal stent against sludge and biofilm formation and stent-induced tissue inflammation.

PubMed

Lee, Tae Hoon; Jang, Bong Seok; Jung, Min Kyo; Pack, Chan Gi; Choi, Jun-Ho; Park, Do Hyun

2016-10-14

To reduce tissue or tumor ingrowth, covered self-expandable metal stents (SEMSs) have been developed. The effectiveness of covered SEMSs may be attenuated by sludge or stone formation or by stent clogging due to the formation of biofilm on the covering membrane. In this study, we tested the hypothesis that a silicone membrane containing silver particles (Ag-P) would prevent sludge and biofilm formation on the covered SEMS. In vitro, the Ag-P-integrated silicone polymer-covered membrane exhibited sustained antibacterial activity, and there was no definite release of silver ions from the Ag-P-integrated silicone polymer membrane at any time point. Using a porcine stent model, in vivo analysis demonstrated that the Ag-P-integrated silicone polymer-covered SEMS reduced the thickness of the biofilm and the quantity of sludge formed, compared with a conventional silicone-covered SEMS. In vivo, the release of silver ions from an Ag-P-integrated silicone polymer-covered SEMS was not detected in porcine serum. The Ag-P-integrated silicone polymer-covered SEMS also resulted in significantly less stent-related bile duct and subepithelium tissue inflammation than a conventional silicone polymer-covered SEMS. Therefore, the Ag-P-integrated silicone polymer-covered SEMS reduced sludge and biofilm formation and stent-induced pathological changes in tissue. This novel SEMS may prolong the stent patency in clinical application.

The enhancement of photovoltaic parameters in dye-sensitized solar cells of nano-crystalline SnO2 by incorporating with large SrTiO3 particles.

PubMed

Aponsu, G M L P; Wijayarathna, T R C K; Perera, I K; Perera, V P S; Siriwardhana, A C P K

2013-05-15

In this paper, the performance of nano-porous electrodes made of a composite material of SrTiO3 and SnO2 are compared with those made of bare SnO2. When these particular devices are analyzed in a comparative mode the results confirmed the enhancement of photovoltaic parameters in the former device. The performance of respective cells were examined by several methods including I-V characteristic measurements, photocurrent action spectra, dark I-V measurements, Mott-Schottky measurements and X-ray diffraction measurements. Even though such improvements in this particular cell could be explicated by the formation of a potential energy barrier of SrTiO3 particles of comparably large width at the SrTiO3/SnO2 interface, the passivation of voids in the SnO2 film by SrTiO3 particles to a certain extent could not be totally ruled out. Besides, high energetic electrons injected by dye molecules move more credibly through mini-bands formed in the chain of nano-crystalline SnO2 particles to the back contact. The blocking of the recombination path and the shifting up of the uppermost electron occupied level of SnO2 accompanying the conduction band edge in the SrTiO3/SnO2 composite film, may have lead to the observed enhancement of the fill factor and photovoltage, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Bacterial growth on a superhydrophobic surface containing silver nanoparticles

NASA Astrophysics Data System (ADS)

Heinonen, S.; Nikkanen, J.-P.; Laakso, J.; Raulio, M.; Priha, O.; Levänen, E.

2013-12-01

The antibacterial effect of silver can be exploited in the food and beverage industry and medicinal applications to reduce biofouling of surfaces. Very small amount of silver ions are enough to destructively affect the metabolism of bacteria. Moreover, superhydrophobic properties could reduce bacterial adhesion to the surface. In this study we fabricated superhydrophobic surfaces that contained nanosized silver particles. The superhydrophobic surfaces were manufactured onto stainless steel as combination of ceramic nanotopography and hydrophobication by fluorosilane. Silver nanoparticles were precipitated onto the surface by a chemical method. The dissolution of silver from the surface was tested in an aqueous environment under pH values of 1, 3, 5, 7, 9, 11 and 13. The pH value was adjusted with nitric acid and ammonia. It was found that dissolution rate of silver increased as the pH of the solution altered from the pH of de-ionized water to lower and higher pH values but dissolution occurred also in de-ionized water. The antimicrobial potential of this coating was investigated using bacterial strains isolated from the brewery equipment surfaces. The results showed that the number of bacteria adhering onto steel surface was significantly reduced (88%) on the superhydrophobic silver containing coating.

Complex conductivity response to silver nanoparticles in partially saturated sand columns

NASA Astrophysics Data System (ADS)

Abdel Aal, Gamal; Atekwana, Estella A.; Werkema, D. Dale

2017-02-01

The increase in the use of nanoscale materials in consumer products has resulted in a growing concern of their potential hazard to ecosystems and public health from their accidental or intentional introduction to the environment. Key environmental, health, and safety research needs include knowledge and methods for their detection, characterization, fate, and transport. Specifically, techniques available for the direct detection and quantification of their fate and transport in the environment are limited. Their small size, high surface area to volume ratio, interfacial, and electrical properties make metallic nanoparticles, such as silver nanoparticles, good targets for detection using electrical geophysical techniques. Here we measured the complex conductivity response to silver nanoparticles in sand columns under varying moisture conditions (0-30%), nanoparticle concentrations (0-10 mg/g), lithology (presence of clay), pore water salinity (0.0275 and 0.1000 S/m), and particle size (35, 90-210 and 1500-2500 nm). Based on the Cole-Cole relaxation models we obtained the chargeability and the time constant. We demonstrate that complex conductivity can detect silver nanoparticles in porous media with the response enhanced by higher concentrations of silver nanoparticles, moisture content, ionic strength, clay content and particle diameter. Quantification of the volumetric silver nanoparticles content in the porous media can also be obtained from complex conductivity parameters based on the strong power law relationships.

Synthesis of pure colloidal silver nanoparticles with high electroconductivity for printed electronic circuits: the effect of amines on their formation in aqueous media.

PubMed

Natsuki, Jun; Abe, Takao

2011-07-01

This paper describes a practical and convenient method to prepare stable colloidal silver nanoparticles for use in printed electronic circuits. The method uses a dispersant and two kinds of reducing agents including 2-(dimethylamino) ethanol (DMAE), which play important roles in the reduction of silver ions in an aqueous medium. The effect of DMAE and dispersant, as well as the factors affecting particle size and morphology are investigated. In the formation of the silver nanoparticles, reduction occurs rapidly at room temperature and the silver particles can be separated easily from the mixture in a short time. In addition, organic solvents are not used. Pure, small and relatively uniform particles with a diameter less than 10 nm can be obtained that exhibit high electroconductivity. The silver nanoparticles are stable, and can be isolated as a dried powder that can be fully redispersed in deionized water. This method of producing colloidal silver nanoparticles will find practical use in electronics applications. Copyright © 2011 Elsevier Inc. All rights reserved.

In vitro studies to show sequestration of matrix metalloproteinases by silver-containing wound care products.

PubMed

Walker, Michael; Bowler, Philip G; Cochrane, Christine A

2007-09-01

Excess or "uncontrolled" proteinase activity in the wound bed has been implicated as one factor that may delay or compromise wound healing. One proteinase group--matrix metalloproteinases--includes collagenases, elastase, and gelatinases and can be endogenous (cell) or exogenous (bacterial) in origin. A study was conducted to assess the ability of five silver-containing wound care products to reduce a known matrix metalloproteinase supernatant concentration in vitro. Four silver-containing wound dressings (a carboxy-methyl cellulose, a nanocrystalline, a hydro-alginate, and a collagen/oxidized regenerated cellulose composite dressing), along with a 0.5% aqueous silver nitrate [w/v] solution and controls for matrix metalloproteinase-2 and matrix metalloproteinase-9 sourced from ex vivo dermal tissue and blood monocytes, respectively, were used. Extracts were separated and purified using gelatine-Sepharose column chromatography and dialysis and polyacrylamide gel electrophoretic zymography was used to analyze specific matrix metalloproteinase activity. All dressings and the solution were shown to sequester both matrix metalloproteinases. The silver-containing carboxy-methyl cellulose dressing showed significantly greater sequestration for matrix metalloproteinase-2 at 6 and 24 hours (P< 0.001) compared to the other treatments. For matrix metalloproteinase-9, both the carboxy-methyl cellulose dressing and the oxidized regenerated cellulose dressing achieved significant sequestration when compared to the other treatments at 24 hours (P <0.001), which was maintained to 48 hours (P < 0.001). Results from this study show that silver-containing dressings are effective in sequestering matrix metalloproteinase-2 and -9 and that this can be achieved without a sacrificial protein (eg, collagen). Although the varying ability of wound dressings to sequester matrix metalloproteinases has been shown in vitro, further in vivo evidence is required to confirm these findings.

Silver Eco-Solvent Ink for Reactive Printing of Polychromatic SERS and SPR Substrates.

PubMed

Dustov, Mavlavi; Golovina, Diana I; Polyakov, Alexander Yu; Goldt, Anastasia E; Eliseev, Andrei A; Kolesnikov, Efim A; Sukhorukova, Irina V; Shtansky, Dmitry V; Grünert, Wolfgang; Grigorieva, Anastasia V

2018-02-09

A new reactive ink based on a silver citrate complex is proposed for a photochemical route to surface-enhanced Raman spectroscopy active substrates with controllable extinction spectra. The drop-cast test of the ink reveals homogeneous nucleation of silver and colloid particle growth originating directly from photochemical in situ reduction in droplets, while the following evaporation of the deposited ink produces small nano- and micron-size particles. The prepared nanostructures and substrates were accurately characterized by electron microscopy methods and optical extinction spectroscopy. Varying the duration of UV irradiation allows tuning the morphology of individual silver nanoparticles forming hierarchical ring structures with numerous "hot spots" for most efficient Raman enhancement. Raman measurements of probe molecules of rhodamine 6G and methylene blue reached the largest signal enhancement of 10⁶ by the resonance effects.

Hydrophobicity of silver surfaces with microparticle geometry

NASA Astrophysics Data System (ADS)

Macko, Ján; Oriňaková, Renáta; Oriňak, Andrej; Kovaľ, Karol; Kupková, Miriam; Erdélyi, Branislav; Kostecká, Zuzana; Smith, Roger M.

2016-11-01

The effect of the duration of the current deposition cycle and the number of current pulses on the geometry of silver microstructured surfaces and on the free surface energy, polarizability, hydrophobicity and thus adhesion force of the silver surfaces has been investigated. The changes in surface hydrophobicity were entirely dependent on the size and density of the microparticles on the surface. The results showed that formation of the silver microparticles was related to number of current pulses, while the duration of one current pulse played only a minor effect on the final surface microparticle geometry and thus on the surface tension and hydrophobicity. The conventional geometry of the silver particles has been transformed to the fractal dimension D. The surface hydrophobicity depended predominantly on the length of the dendrites not on their width. The highest silver surface hydrophobicity was observed on a surface prepared by 30 current pulses with a pulse duration of 1 s, the lowest one when deposition was performed by 10 current pulses with a duration of 0.1 s. The partial surface tension coefficients γDS and polarizability kS of the silver surfaces were calculated. Both parameters can be applied in future applications in living cells adhesion prediction and spectral method selection. Silver films with microparticle geometry showed a lower variability in final surface hydrophobicity when compared to nanostructured surfaces. The comparisons could be used to modify surfaces and to modulate human cells and bacterial adhesion on body implants, surgery instruments and clean surfaces.

Impact of moderate silver carp biomass gradient on zooplankton communities in a eutrophic reservoir. Consequences for the use of silver carp in biomanipulation.

PubMed

Domaizon, I; Dévaux, J

1999-07-01

We examined the impacts of moderate gradient silver carp biomass (five levels from 0 to 36 g.m-3, i.e. about 0-792 kg.ha-1) on zooplankton communities of the eutrophic Villerest reservoir (France). During our mesocosm experiment changes in zooplankton assemblages were dependent on silver carp biomass. In the fishless and low fish biomass treatments, zooplankton abundance increased through time, owing to a peak in cladoceran density, but decreased (mainly cladocerans) at highest fish biomass. Copepods and rotifers were less affected at the highest fish biomass and dominated zooplankton communities. We highlighted that the presence of high silver carp biomass could lead to changes in phytoplankton assemblage via the impact on herbivorous zooplankton. Since silver carp efficiently graze on particles > 20 microns, the suppression of herbivorous cladocerans could result in an increase in small size algae (< 20 microns) abundance since these species would be released from grazers as well as competitors (large algae grazed by silver carp) and nutrients levels would be enhanced by fish internal loading. Our results showed that the use of low silver carp biomass (< 200 kg.ha-1) would allow us to minimize these negative effects.

Method to produce nanocrystalline powders of oxide-based phosphors for lighting applications

DOEpatents

Loureiro, Sergio Paulo Martins; Setlur, Anant Achyut; Williams, Darryl Stephen; Manoharan, Mohan; Srivastava, Alok Mani

2007-12-25

Some embodiments of the present invention are directed toward nanocrystalline oxide-based phosphor materials, and methods for making same. Typically, such methods comprise a steric entrapment route for converting precursors into such phosphor material. In some embodiments, the nanocrystalline oxide-based phosphor materials are quantum splitting phosphors. In some or other embodiments, such nanocrystalline oxide based phosphor materials provide reduced scattering, leading to greater efficiency, when used in lighting applications.

Thiourea leaching gold and silver from the printed circuit boards of waste mobile phones.

PubMed

Jing-ying, Li; Xiu-li, Xu; Wen-quan, Liu

2012-06-01

The present communication deals with the leaching of gold and silver from the printed circuit boards (PCBs) of waste mobile phones using an effective and less hazardous system, i.e., a thiourea leaching process as an alternative to the conventional and toxic cyanide leaching of gold. The influence of particle size, thiourea and Fe(3+) concentrations and temperature on the leaching of gold and silver from waste mobile phones was investigated. Gold extraction was found to be enhanced in a PCBs particle size of 100 mesh with the solutions containing 24 g/L thiourea and Fe(3+) concentration of 0.6% under the room temperature. In this case, about 90% of gold and 50% of silver were leached by the reaction of 2h. The obtained data will be useful for the development of processes for the recycling of gold and silver from the PCBs of waste mobile phones. Copyright © 2012 Elsevier Ltd. All rights reserved.

Methylcellulose-Directed Synthesis of Nanocrystalline Zeolite NaA with High CO₂ Uptake.

PubMed

Shakarova, Dilshod; Ojuva, Arto; Bergström, Lennart; Akhtar, Farid

2014-07-28

Zeolite NaA nanocrystals with a narrow particle size distribution were prepared by template-free hydrothermal synthesis in thermo-reversible methylcellulose gels. The effects of the amount of methylcellulose, crystallization time and hydrothermal treatment temperature on the crystallinity and particle size distribution of the zeolite NaA nanocrystals were investigated. We found that the thermogelation of methylcellulose in the alkaline Na₂O-SiO₂-Al₂O₃-H₂O system played an important role in controlling the particle size. The synthesized zeolite nanocrystals are highly crystalline, as demonstrated by X-ray diffraction (XRD), and scanning electron microscopy (SEM) shows that the nanocrystals can also display a well-defined facetted morphology. Gas adsorption studies on the synthesized nanocrystalline zeolite NaA showed that nanocrystals with a size of 100 nm displayed a high CO₂ uptake capacity (4.9 mmol/g at 293 K at 100 kPa) and a relatively rapid uptake rate compared to commercially available, micron-sized particles. Low-cost nanosized zeolite adsorbents with a high and rapid uptake are important for large scale gas separation processes, e.g., carbon capture from flue gas.

Silver(II) Oxide or Silver(I,III) Oxide?

ERIC Educational Resources Information Center

Tudela, David

2008-01-01

The often called silver peroxide and silver(II) oxide, AgO or Ag[subscript 2]O[subscript 2], is actually a mixed oxidation state silver(I,III) oxide. A thermochemical cycle, with lattice energies calculated within the "volume-based" thermodynamic approach, explain why the silver(I,III) oxide is more stable than the hypothetical silver(II) oxide.…

Catharanthus roseus: a natural source for the synthesis of silver nanoparticles

PubMed Central

Mukunthan, KS; Elumalai, EK; Patel, Trupti N; Murty, V Ramachandra

2011-01-01

Objective To develop a simple rapid procedure for bioreduction of silver nanoparticles (AgNPs) using aqueous leaves extracts of Catharanthus roseus (C. roseus). Methods Characterization were determined by using UV-Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive X-ray and X-ray diffraction. Results SEM showed the formation of silver nanoparticles with an average size of 67 nm to 48 nm. X-ray diffraction analysis showed that the particles were crystalline in nature with face centered cubic geometry. Conclusions C. roseus demonstrates strong potential for synthesis of silver nanoparticles by rapid reduction of silver ions (Ag+ to Ag0). This study provides evidence for developing large scale commercial production of value-added products for biomedical/nanotechnology-based industries. PMID:23569773

Effect of the size of silver nanoparticles on SERS signal enhancement

NASA Astrophysics Data System (ADS)

He, Rui Xiu; Liang, Robert; Peng, Peng; Norman Zhou, Y.

2017-08-01

The localized surface plasmon resonance arising from plasmonic materials is beneficial in solution-based and thin-film sensing applications, which increase the sensitivity of the analyte being tested. Silver nanoparticles from 35 to 65 nm in diameter were synthesized using a low-temperature method and deposited in a monolayer on a (3-aminopropyl)triethoxysilane (APTES)-functionalized glass slide. The effect of particle size on monolayer structure, optical behavior, and surface-enhanced Raman scattering (SERS) is studied. While increasing particle size decreases particle coverage, it also changes the localized surface plasmon resonance and thus the SERS activity of individual nanoparticles. Using a laser excitation wavelength of 633 nm, the stronger localized surface plasmon resonance coupling to this excitation wavelength at larger particle sizes trumps the loss in surface coverage, and greater SERS signals are observed. The SERS signal enhancement accounts for the higher SERS signal, which was verified using a finite element model of a silver nanoparticle dimer with various nanoparticle sizes and separation distances.

Toxicity of nano- and micro-sized silver particles in human hepatocyte cell line L02

NASA Astrophysics Data System (ADS)

Liu, Pengpeng; Guan, Rongfa; Ye, Xingqian; Jiang, Jiaxin; Liu, Mingqi; Huang, Guangrong; Chen, Xiaoting

2011-07-01

Silver nanoparticles (Ag NPs) previously classified as antimicrobial agents have been widely used in consumers and industrial products, especially food storage material. Ag NPs used as antimicrobial agents may be found in liver. Thus, examination of the ability of Ag NPs to penetrate the liver is warranted. The aim of the study was to determine the optimal viability assay for using with Ag NPs in order to assess their toxicity to liver cells. For toxicity evaluations, cellular morphology, mitochondrial function (3-(4, 5-dimethylazol-2-yl)-2, 5-diphenyl-tetrazolium bromide, MTT assay), membrane leakage of lactate dehydrogenase (lactate dehydrogenase, LDH release assay), Oxidative stress markers (malonaldehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD)), DNA damage (single cell gel eletrophoresis, SCGE assay), and protein damage were assessed under control and exposed conditions (24 h of exposure). The results showed that mitochondrial function decreased significantly in cells exposed to Ag NPs at 25 μg·mL-1. LDH leakage significantly increased in cells exposed to Ag NPs (>= 25 μg mL-1) while micro-sized silver particles tested displayed LDH leakage only at higher doses (100 μg·mL-1). The microscopic studies demonstrated that nanoparticle-exposed cells at higher doses became abnormal in size, displaying cellular shrinkage, and an acquisition of an irregular shape. Due to toxicity of silver, further study conducted with reference to its oxidative stress. The results exhibited significant depletion of GSH level, increase in SOD levels and lead to lipid peroxidation, which suggested that cytotoxicity of Ag NPs in liver cells might be mediated through oxidative stress. The results demonstrates that Ag NPs lead to cellular morphological modifications, LDH leakage, mitochondrial dysfunction, and cause increased generation of ROS, depletion of GSH, lipid peroxidation, oxidative DNA damage and protein damage. Though the exact mechanism behind Ag NPs

Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

NASA Astrophysics Data System (ADS)

Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

2017-12-01

Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

Three-dimensional analysis by electron diffraction methods of nanocrystalline materials.

PubMed

Gammer, Christoph; Mangler, Clemens; Karnthaler, Hans-Peter; Rentenberger, Christian

2011-12-01

To analyze nanocrystalline structures quantitatively in 3D, a novel method is presented based on electron diffraction. It allows determination of the average size and morphology of the coherently scattering domains (CSD) in a straightforward way without the need to prepare multiple sections. The method is applicable to all kinds of bulk nanocrystalline materials. As an example, the average size of the CSD in nanocrystalline FeAl made by severe plastic deformation is determined in 3D. Assuming ellipsoidal CSD, it is deduced that the CSD have a width of 19 ± 2 nm, a length of 18 ± 1 nm, and a height of 10 ± 1 nm.

Anisotropy induced in a silver chloride emulsion by two successive beams of white light perpendicularly polarized

NASA Astrophysics Data System (ADS)

Attia, Mondher; Debrus, Solange; Henriot, M. P.; May, Marie

1983-04-01

This paper is a study of the anisotropy induced in a silver chloride photographic emulsion by two successive beams of white light, linearly polarized at right angle. After the first exposure, the colloidal medium contains silver ellipsoids e generated by the photolysis of silver chloride and silver ellipsoids e b resulting of the partial destruction of some of the previous ones by long wavelengths. This medium is then illuminated by the second beam linearly polarized at right angle of the first beam. Short wavelengths induced silver ellipsoids e' identical to the ellopsoids e but rotated through π/2 with respect to them. As in the first exposure, some of them are partly broken up and transformed into ellipsoids e' b identical to ellipsoids e b but the direction of their major axis. Moreover, the long wavelengths of second exposure transform some of the particles e and e b generated during the first exposure, into smaller ellipsoids e eb and e bb. Finally, the colloidal medium resulting of these two exposures, contains silver chloride and six sorts of silver particles. By calculating the indices of the medium, we show that the wavelengths characterizing the zero birefringence and zero dichroism of the emulsion are dependent on the energies recorded during each of the exposures.

Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

NASA Astrophysics Data System (ADS)

Marvel, Christopher Jonathan

diffusivity calculations conceptually suggested that increasing W alloying concentrations can decrease the grain growth rate. The strongest evidence of grain growth stagnation was via nanoscale oxide particle drag in highly contaminated electrodeposited alloys. Interestingly, W-segregation was also detected to the oxide phase boundaries and revealed a potential indirect mechanism of thermal stability. The phase stability of pure and contaminated Ni-W alloys was investigated with density functional theory. Primarily, the calculations suggested that the intermetallic phases NiW and NiW2 are thermodynamically unstable, meaning the binary phase diagram is incorrect, but the ternary carbides Ni 6W6C and Ni2W4C are stable. Several Ni-W binary and Ni-W-C ternary phase diagrams were constructed using a simplified CALPHAD approach to improve the understanding of Ni-W phase stability. Lastly, it was determined that the fabrication process greatly influences the impurity types and concentrations of the alloys, and therefore greatly dictate which thermal stability mechanisms are active. Mechanically alloyed samples were found to be the most resistant to grain growth. The findings of this research will hopefully guide future efforts to design more thermally stable nanocrystalline alloys. The link between phase stability and grain growth behavior of Ni-W was thoroughly discussed, as well as the dependence of bulk fabrication processing on the contamination found in the alloys. Ultimately, this research has greatly expanded the general understanding of nanocrystalline Ni-W microstructures, and it is likely that similar phenomena occur in other nanocrystalline systems.

Electroless growth of silver nanoparticles into mesostructured silica block copolymer films.

PubMed

Bois, Laurence; Chassagneux, Fernand; Desroches, Cédric; Battie, Yann; Destouches, Nathalie; Gilon, Nicole; Parola, Stéphane; Stéphan, Olivier

2010-06-01

Silver nanoparticles and silver nanowires have been grown inside mesostructured silica films obtained from block copolymers using two successive reduction steps: the first one involves a sodium borohydride reduction or a photoreduction of silver nitrate contained in the film, and the second one consists of a silver deposit on the primary nanoparticles, carried out by silver ion solution reduction with hydroxylamine chloride. We have demonstrated that the F127 block copolymer ((PEO)(106)(PPO)(70)(PEO)(106)), "F type", mesostructured silica film is a suitable "soft" template for the fabrication of spherical silver nanoparticles arrays. Silver spheres grow from 7 to 11 nm upon the second reduction step. As a consequence, a red shift of the surface plasmon resonance associated with metallic silver has been observed and attributed to plasmonic coupling between particles. Using a P123 block copolymer ((PEO)(20)(PPO)(70)(PEO)(20)), "P type", mesostructured silica film, we have obtained silver nanowires with typical dimension of 10 nm x 100 nm. The corresponding surface plasmon resonance is blue-shifted. The hydroxylamine chloride treatment appears to be efficient only when a previous chemical reduction is performed, assuming that the first sodium borohydride reduction induces a high concentration of silver nuclei in the first layer of the porous silica (film/air interface), which explains their reactivity for further growth.

Nanocrystalline copper films are never flat

NASA Astrophysics Data System (ADS)

Zhang, Xiaopu; Han, Jian; Plombon, John J.; Sutton, Adrian P.; Srolovitz, David J.; Boland, John J.

2017-07-01

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy.

Syntheses of nanocrystalline BaTiO3 and their optical properties

NASA Astrophysics Data System (ADS)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

Nano-silver in drinking water and drinking water sources: stability and influences on disinfection by-product formation.

PubMed

Tugulea, A-M; Bérubé, D; Giddings, M; Lemieux, F; Hnatiw, J; Priem, J; Avramescu, M-L

2014-10-01

Nano-silver is increasingly used in consumer products from washing machines and refrigerators to devices marketed for the disinfection of drinking water or recreational water. The nano-silver in these products may be released, ending up in surface water bodies which may be used as drinking water sources. Little information is available about the stability of the nano-silver in sources of drinking water, its fate during drinking water disinfection processes, and its interaction with disinfection agents and disinfection by-products (DBPs). This study aims to investigate the stability of nano-silver in drinking water sources and in the finished drinking water when chlorine and chloramines are used for disinfection and to observe changes in the composition of DBPs formed when nano-silver is present in the source water. A dispersion of nano-silver particles (10 nm; PVP-coated) was used to spike untreated Ottawa River water, treated Ottawa River water, organic-free water, and a groundwater at concentrations of 5 mg/L. The diluted dispersions were kept under stirred and non-stirred conditions for up to 9 months and analyzed weekly using UV absorption to assess the stability of the nano-silver particles. In a separate experiment, Ottawa River water containing nano-silver particles (at 0.1 and 1 mg/L concentration, respectively) was disinfected by adding sodium hypochlorite (a chlorinating agent) in sufficient amounts to maintain a free chlorine residual of approximately 0.4 mg/L after 24 h. The disinfected drinking water was then quenched with ascorbic acid and analyzed for 34 neutral DBPs (trihalomethanes, haloacetonitriles, haloacetaldehydes, 1,1 dichloro-2-propanone, 1,1,1 trichloro-2-propanone, chloropicrin, and cyanogen chloride). The results were compared to the profile of DBPs obtained under the same conditions in the absence of nano-silver and in the presence of an equivalent concentration of Ag(+) ions (as AgNO3). The stability of the nano-silver dispersions in

Emission Behavior of Fluorescently Labeled Silver Nanoshell: Enhanced Self-Quenching by Metal Nanostructure.

PubMed

Zhang, Jian; Fu, Yi; Lakowicz, Joseph R

2007-02-08

Labeled silica beads with an average diameter of 100 nm were synthesized by incorporating with 20-600 μM Ru(bpy)(3) (2+) complexes. Silver shells were deposited on the beads layer-by-layer with the shell thickness of 5-50 nm. The emission band became narrower and the intensity was enhanced depending on the shell thickness. Self-quenching of the probe was observed at high concentration. Poisson statistics were employed to analyze self-quenching of the fluorophores. The estimated quenching distance was extended from 6 to 16 nm with shell growth from 0 to 50 nm. Moreover, the silver shells were also labeled with Rhodamine 6G. Fluorescence enhancement and reduced lifetime were also observed for silver-silica shell containing R6G. We found that by adjustment of probe concentration and silver shell thickness, a Ru(bpy)(3) (2+)-labeled particle could be 600 times brighter than an isolated Ru(bpy)(3) (2+) molecule. We expect labeled metal core-shell structures can become useful probes for high sensitivity and/or single particle assay.

Distinctive glial and neuronal interfacing on nanocrystalline diamond.

PubMed

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth.

Distinctive Glial and Neuronal Interfacing on Nanocrystalline Diamond

PubMed Central

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth. PMID:24664111

Biocompatible nanocrystalline natural bonelike carbonated hydroxyapatite synthesized by mechanical alloying in a record minimum time.

PubMed

Lala, S; Brahmachari, S; Das, P K; Das, D; Kar, T; Pradhan, S K

2014-09-01

Single phase nanocrystalline biocompatible A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4.2H2O powders in open air at room temperature within 2h of milling. The A-type carbonation in HAp is confirmed by FTIR analysis. Structural and microstructure parameters of as-milled powders are obtained from both Rietveld's powder structure refinement analysis and transmission electron microscopy. Size and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Mechanical alloying causes amorphization of a part of crystalline A-cHAp which is analogous to native bone mineral. Some primary bond lengths of as-milled samples are critically measured. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of biological apatite. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of silver, cesium, and strontium release predictions using PARFUME with results from the AGR-1 irradiation experiment

DOE PAGES

Collin, Blaise P.; Petti, David A.; Demkowicz, Paul A.; ...

2015-08-22

Here, the PARFUME (PARticle FUel ModEl) code was used to predict the release of fission products silver, cesium, and strontium from tristructural isotropic coated fuel particles and compacts during the first irradiation experiment (AGR-1) of the Advanced Gas Reactor Fuel Development and Qualification program. The PARFUME model for the AGR-1 experiment used the fuel compact volume average temperature for each of the 620 days of irradiation to calculate the release of silver, cesium, and strontium from a representative particle for a select number of AGR-1 compacts. Post-irradiation examination measurements provided data on release of these fission products from fuel compactsmore » and fuel particles, and retention of silver in the compacts outside of the silicon carbide (SiC) layer. PARFUME-predicted fractional release of silver, cesium, and strontium was determined and compared to the PIE measurements. For silver, comparisons show a trend of over-prediction at low burnup and under-prediction at high burnup. PARFUME has limitations in the modeling of the temporal and spatial distributions of the temperature and burnup across the compacts, which affects the accuracy of its predictions. Nevertheless, the comparisons on silver release lie in the same order of magnitude. Results show an overall over-prediction of the fractional release of cesium by PARFUME. For particles with failed SiC layers, the over-prediction is by a factor of up to 3, corresponding to a potential over-estimation of the diffusivity in uranium oxycarbide (UCO) by a factor of up to 250. For intact particles, whose release is much lower, the over-prediction is by a factor of up to 100, which could be attributed to an over-estimated diffusivity in SiC by about 40% on average. The release of strontium from intact particles is also over-predicted by PARFUME, which also points towards an over-estimated diffusivity of strontium in either SiC or UCO, or possibly both. The measured strontium fractional

Comparison of silver, cesium, and strontium release predictions using PARFUME with results from the AGR-1 irradiation experiment

NASA Astrophysics Data System (ADS)

Collin, Blaise P.; Petti, David A.; Demkowicz, Paul A.; Maki, John T.

2015-11-01

The PARFUME (PARticle FUel ModEl) code was used to predict the release of fission products silver, cesium, and strontium from tristructural isotropic coated fuel particles and compacts during the first irradiation experiment (AGR-1) of the Advanced Gas Reactor Fuel Development and Qualification program. The PARFUME model for the AGR-1 experiment used the fuel compact volume average temperature for each of the 620 days of irradiation to calculate the release of silver, cesium, and strontium from a representative particle for a select number of AGR-1 compacts. Post-irradiation examination (PIE) measurements provided data on release of these fission products from fuel compacts and fuel particles, and retention of silver in the compacts outside of the silicon carbide (SiC) layer. PARFUME-predicted fractional release of silver, cesium, and strontium was determined and compared to the PIE measurements. For silver, comparisons show a trend of over-prediction at low burnup and under-prediction at high burnup. PARFUME has limitations in the modeling of the temporal and spatial distributions of the temperature and burnup across the compacts, which affects the accuracy of its predictions. Nevertheless, the comparisons on silver release lie in the same order of magnitude. Results show an overall over-prediction of the fractional release of cesium by PARFUME. For particles with failed SiC layers, the over-prediction is by a factor of up to 3, corresponding to a potential over-estimation of the diffusivity in uranium oxycarbide (UCO) by a factor of up to 250. For intact particles, whose release is much lower, the over-prediction is by a factor of up to 100, which could be attributed to an over-estimated diffusivity in SiC by about 40% on average. The release of strontium from intact particles is also over-predicted by PARFUME, which also points towards an over-estimated diffusivity of strontium in either SiC or UCO, or possibly both. The measured strontium fractional release

Methods for producing monodispersed particles of barium titanate

DOEpatents

Hu, Zhong-Cheng

2001-01-01

The present invention is a low-temperature controlled method for producing high-quality, ultrafine monodispersed nanocrystalline microsphere powders of barium titanate and other pure or composite oxide materials having particles ranging from nanosized to micronsized particles. The method of the subject invention comprises a two-stage process. The first stage produces high quality monodispersed hydrous titania microsphere particles prepared by homogeneous precipitation via dielectric tuning in alcohol-water mixed solutions of inorganic salts. Titanium tetrachloride is used as an inorganic salt precursor material. The second stage converts the pure hydrous titania microsphere particles into crystalline barium titanate microsphere powders via low-temperature, hydrothermal reactions.

Demonstration of vessels in CNS and other organs by AMG silver enhancement of colloidal gold particles dispersed in gelatine.

PubMed

Danscher, G; Andreasen, A

1997-12-01

We present a new autometallographic technique for demonstrating vessels and other small cavities at light microscopy (LM) and electron microscopy (EM) levels. It is possible to obtain detailed knowledge of the 3-D appearance of the vascular system by exchanging blood with a 40 degrees C, 8% gelatine solution containing colloidal gold particles (gold gelatine solution, GGS) and ensuing silver enhancement of the gold particles by autometallography (AMG). The GGS-AMG technique demonstrates the vascular system as a dark web that can be studied in cryostat, vibratome, methacrylate, paraffin and Epon sections at all magnifications. The infused GGS becomes increasingly viscous and finally becomes rigid when the temperature falls below 20 degrees C. An additional advantage of this technique is the fact that none of the tested counterstains or immunotechniques interfere with this AMG approach. The GGS-AMG technique is demonstrated on rat brains but can be applied to any organ. We believe that the present technique is valuable for both experimental studies and routine pathology.

Single particle ICP-MS characterization of titanium dioxide, silver, and gold nanoparticles during drinking water treatment.

PubMed

Donovan, Ariel R; Adams, Craig D; Ma, Yinfa; Stephan, Chady; Eichholz, Todd; Shi, Honglan

2016-02-01

One of the most direct means for human exposure to nanoparticles (NPs) released into the environment is drinking water. Therefore, it is critical to understand the occurrence and fate of NPs in drinking water systems. The objectives of this study were to develop rapid and reliable analytical methods and apply them to investigate the fate and transportation of NPs during drinking water treatments. Rapid single particle ICP-MS (SP-ICP-MS) methods were developed to characterize and quantify titanium-containing, titanium dioxide, silver, and gold NP concentration, size, size distribution, and dissolved metal element concentration in surface water and treated drinking water. The effectiveness of conventional drinking water treatments (including lime softening, alum coagulation, filtration, and disinfection) to remove NPs from surface water was evaluated using six-gang stirrer jar test simulations. The selected NPs were nearly completely (97 ± 3%) removed after lime softening and alum coagulation/activated carbon adsorption treatments. Additionally, source and drinking waters from three large drinking water treatment facilities utilizing similar treatments with the simulation test were collected and analyzed by the SP-ICP-MS methods. Ti-containing particles and dissolved Ti were present in the river water samples, but Ag and Au were not present. Treatments used at each drinking water treatment facility effectively removed over 93% of the Ti-containing particles and dissolved Ti from the source water. Copyright © 2015 Elsevier Ltd. All rights reserved.

Extreme creep resistance in a microstructurally stable nanocrystalline alloy

NASA Astrophysics Data System (ADS)

Darling, K. A.; Rajagopalan, M.; Komarasamy, M.; Bhatia, M. A.; Hornbuckle, B. C.; Mishra, R. S.; Solanki, K. N.

2016-09-01

Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10-6 per second—six to eight orders of magnitude lower than most nanocrystalline metals—at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

Nanocrystalline ordered vanadium carbide: Superlattice and nanostructure

NASA Astrophysics Data System (ADS)

Kurlov, A. S.; Gusev, A. I.; Gerasimov, E. Yu.; Bobrikov, I. A.; Balagurov, A. M.; Rempel, A. A.

2016-02-01

The crystal structure, micro- and nanostructure of coarse- and nanocrystalline powders of ordered vanadium carbide V8C7 have been examined by X-ray and neutron diffraction and electron microscopy methods. The synthesized coarse-crystalline powder of ordered vanadium carbide has flower-like morphology. It was established that the real ordered phase has the composition V8C7-δ (δ ≅ 0.03) deviating from perfect stoichiometric composition V8C7. The vanadium atoms forming the octahedral environment □V6 of vacant sites in V8C7-δ are displaced towards the vacancy □. The presence of carbon onion-like structures was found in the vanadium carbide powders with a small content of free (uncombined) carbon. The nanopowders of V8C7-δ carbide with average particle size of 20-30 nm produced by high-energy milling of coarse-crystalline powder retain the crystal structure of the initial powder, but differ in the lattice deformation distortion anisotropy.

Plane shock loading on mono- and nano-crystalline silicon carbide

NASA Astrophysics Data System (ADS)

Branicio, Paulo S.; Zhang, Jingyun; Rino, José P.; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya

2018-03-01

The understanding of the nanoscale mechanisms of shock damage and failure in SiC is essential for its application in effective and damage tolerant coatings. We use molecular-dynamics simulations to investigate the shock properties of 3C-SiC along low-index crystallographic directions and in nanocrystalline samples with 5 nm and 10 nm grain sizes. The predicted Hugoniot in the particle velocity range of 0.1 km/s-6.0 km/s agrees well with experimental data. The shock response transitions from elastic to plastic, predominantly deformation twinning, to structural transformation to the rock-salt phase. The predicted strengths from 12.3 to 30.9 GPa, at the Hugoniot elastic limit, are in excellent agreement with experimental data.

Silver Eco-Solvent Ink for Reactive Printing of Polychromatic SERS and SPR Substrates

PubMed Central

Dustov, Mavlavi; Goldt, Anastasia E.; Sukhorukova, Irina V.; Grünert, Wolfgang; Grigorieva, Anastasia V.

2018-01-01

A new reactive ink based on a silver citrate complex is proposed for a photochemical route to surface-enhanced Raman spectroscopy active substrates with controllable extinction spectra. The drop-cast test of the ink reveals homogeneous nucleation of silver and colloid particle growth originating directly from photochemical in situ reduction in droplets, while the following evaporation of the deposited ink produces small nano- and micron-size particles. The prepared nanostructures and substrates were accurately characterized by electron microscopy methods and optical extinction spectroscopy. Varying the duration of UV irradiation allows tuning the morphology of individual silver nanoparticles forming hierarchical ring structures with numerous “hot spots” for most efficient Raman enhancement. Raman measurements of probe molecules of rhodamine 6G and methylene blue reached the largest signal enhancement of 106 by the resonance effects. PMID:29425119

Surface plasmon effect in electrodeposited diamond-like carbon films for photovoltaic application

NASA Astrophysics Data System (ADS)

Ghosh, B.; Ray, Sekhar C.; Espinoza-González, Rodrigo; Villarroel, Roberto; Hevia, Samuel A.; Alvarez-Vega, Pedro

2018-04-01

Diamond-like carbon (DLC) films and nanocrystalline silver particles containing diamond-like carbon (DLC:Ag) films were electrodeposited on n-type silicon substrate (n-Si) to prepare n-Si/DLC and n-Si/DLC:Ag heterostructures for photovoltaic (PV) applications. Surface plasmon resonance (SPR) effect in this cell structure and its overall performance have been studied in terms of morphology, optical absorption, current-voltage characteristics, capacitance-voltage characteristics, band diagram and external quantum efficiency measurements. Localized surface plasmon resonance effect of silver nanoparticles (Ag NPs) in n-Si/DLC:Ag PV structure exhibited an enhancement of ∼28% in short circuit current density (JSC), which improved the overall efficiency of the heterostructures.

Luminescence and related properties of nanocrystalline porous silicon

NASA Astrophysics Data System (ADS)

Koshida, N.

This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

Analysis of silver nanoparticles in antimicrobial products using surface-enhanced Raman spectroscopy (SERS).

PubMed

Guo, Huiyuan; Zhang, Zhiyun; Xing, Baoshan; Mukherjee, Arnab; Musante, Craig; White, Jason C; He, Lili

2015-04-07

Silver nanoparticles (AgNPs) are the most commonly used nanoparticles in consumer products. Concerns over human exposure to and risk from these particles have resulted in increased interest in novel strategies to detect AgNPs. This study investigated the feasibility of surface-enhanced Raman spectroscopy (SERS) as a method for the detection and quantification of AgNPs in antimicrobial products. By using ferbam (ferric dimethyl-dithiocarbamate) as an indicator molecule that binds strongly onto the nanoparticles, AgNPs detection and discrimination were achieved based on the signature SERS response of AgNPs-ferbam complexes. SERS response with ferbam was distinct for silver ions, silver chloride, silver bulk particles, and AgNPs. Two types of AgNPs with different coatings, citrate and polyvinylpirrolidone (PVP), both showed strong interactions with ferbam and induced strong SERS signals. SERS was effectively applicable for detecting Ag particles ranging from 20 to 200 nm, with the highest signal intensity in the 60-100 nm range. A linear relationship (R(2) = 0.9804) between Raman intensity and citrate-AgNPs concentrations (60 nm; 0-20 mg/L) indicates the potential for particle quantification. We also evaluated SERS detection of AgNPs in four commercially available antimicrobial products. Combined with ICP-MS and TEM data, the results indicated that the SERS response is primarily dependent on size, but also affected by AgNPs concentration. The findings demonstrate that SERS is a promising analytical platform for studying environmentally relevant levels of AgNPs in consumer products and related matrices.

A Novel Photosynthesis of Carboxymethyl Starch-Stabilized Silver Nanoparticles

PubMed Central

El-Sheikh, M. A.

2014-01-01

The water soluble photoinitiator (PI) 4-(trimethyl ammonium methyl) benzophenone chloride is used for the first time in the synthesis of silver nanoparticles (AgNPs). A new green synthesis method involves using PI/UV system, carboxymethyl starch (CMS), silver nitrate, and water. A mechanism of the reduction of silver ions to AgNPs by PI/UV system as well as by the newly born aldehydic groups was proposed. The synthesis process was assessed by UV-vis spectra and TEM of AgNPs colloidal solution. The highest absorbance was obtained using CMS, PI and AgNO3 concentrations of 10 g/L, 1 g/L, and 1 g/L, respectively; 40°C; 60 min; pH 7; and a material : liquor ratio 1 : 20. AgNPs so-obtained were stable in aqueous solution over a period of three weeks at room temperature (~25°C) and have round shape morphology. The sizes of synthesized AgNPs were in the range of 1–21 nm and the highest counts % of these particles were for particles of 6–10 and 1–3 nm, respectively. PMID:24672325

Method for the recovery of silver from silver zeolite

DOEpatents

Reimann, G.A.

1985-03-05

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

Method for the recovery of silver from silver zeolite

DOEpatents

Reimann, George A.

1986-01-01

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

Fluorescence enhancement on silver nanostructures: studies of components of ribosomal translation in vitro

NASA Astrophysics Data System (ADS)

Mandecki, Wlodek; Bharill, Shashank; Borejdo, Julian; Cabral, Diana; Cooperman, Barry S.; Farrell, Ian; Fetter, Linus; Goldman, Emanuel; Gryczynski, Zygmunt; Jakubowski, Hieronim; Liu, Hanqing; Luchowski, Rafal; Matveeva, Evgenia; Pan, Dongli; Qin, Haiou; Tennant, Donald; Gryczynski, Ignacy

2008-02-01

Metallic particles, silver in particular, can significantly enhance the fluorescence of dye molecules in the immediate vicinity (5-20 nm) of the particle. This magnifying effect can be theoretically explained/predicted by considering the change of photonic mode density near the fluorophore due to coupling to the conducting surface. We are using this method to observe fluorescence from a single ribosomal particle in a project aimed at acquiring sequence information from the translating ribosome (NIH's $1000 Genome Initiative). Several quartz slides with silver nanostructures were made using electron beam lithography techniques. The structures were approximately 50 nm high silver tiles measuring 400-700 nm on the side, and were spaced differently over a total area of 1 mm x 1 mm on any given quartz slide. In a preliminary experiment, we coated this surface with the Alexa 647-labeled antibodies and collected single molecule images using the MicroTime 200 (PicoQuant) confocal system. We showed that the fluorescence intensity measured over the silver islands film was more than 100-fold higher than fluorescence from a comparable site on uncoated section of the quartz slide. No noticeable photobleaching was seen. The fluorescence lifetime was very short, about 200 ps or less (this is the resolution limit of the system). The method has great promise for investigations of biologically relevant single molecules.

Study of the spectra of silica colloidal crystals with assembled silver obtained from a photolysis method

NASA Astrophysics Data System (ADS)

Li, Wenjiang; He, Jinglong; He, Sailing

2005-02-01

The colorful artificial 3D silica colloidal crystals (opal) were prepared through self-assembly of silica spheres in the visible frequency range. We directly synthesized nano silver particles in the void of the silica artificial opal film using the photolysis of silver nitrate under UV light, nano silver particles were self-deposited around the surface of silica sphere. The shifts of the stop band of the artificial crystals after exposing different time under UV light were studied. Synthetic silica opal with three-dimensional (3D) structure is potentially useful for the development of diffractive optical devices, micro mechanical systems, and sensory elements because photonic band gaps obtained from self-assembled closely packed periodic structures.

Gigacycle fatigue behavior by ultrasonic nanocrystalline surface modification.

PubMed

Ahn, D G; Amanov, A; Cho, I S; Shin, K S; Pyoun, Y S; Lee, C S; Park, I G

2012-07-01

Nanocrystalline surface layer up to 84 microm in thick is produced on a specimen made of Al6061-T6 alloy by means of surface treatment called ultrasonic nanocrystalline surface modification (UNSM) technique. The refined grain size is produced in the top-layer and it is increased with increasing depth from the top surface. Vickers microhardness measurement for each nanocrystalline surface layer is performed and measurement results showed that the microhardness is increased from 116 HV up to 150 HV, respectively. In this study, fatigue behavior of Al6061-T6 alloy was studied up to 10(7)-10(9) cycles by using a newly developed ultrasonic fatigue testing (UFT) rig. The fatigue results of the UNSM-treated Al6061-T6 alloy specimens were compared with those of the untreated specimens. The microstructure of the untreated and UNSM-treated specimens was characterized by means of scanning electron microscopey (SEM) and transmission electron microscopey (TEM).

Silver nanoparticles are broad-spectrum bactericidal and virucidal compounds

PubMed Central

2011-01-01

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

Silver Nanoparticle Impregnated Bio-Based Activated Carbon with Enhanced Antimicrobial Activity

NASA Astrophysics Data System (ADS)

Selvakumar, R.; Suriyaraj, S. P.; Jayavignesh, V.; Swaminathan, K.

2013-08-01

The present study involves the production of silver nanoparticles using a novel yeast strain Saccharomyces cerevisiae BU-MBT CY-1 isolated from coconut cell sap. The biological reduction of silver nitrate by the isolate was deducted at various time intervals. The yeast cells after biological silver reduction were harvested and subjected to carbonization at 400°C for 1 h and its properties were analyzed using Fourier transform infra-red spectroscopy, X-ray diffraction, scanning electron microscope attached with energy dispersive spectroscopy and transmission electron microscopy. The average size of the silver nanoparticles present on the surface of the carbonized silver containing yeast cells (CSY) was 19 ± 9 nm. The carbonized control yeast cells (CCY) did not contain any particles on its surface. The carbonized silver nanoparticles containing yeast cells (CSY) were made into bioactive emulsion and tested for its efficacy against various pathogenic Gram positive and Gram negative bacteria. The antimicrobial activity studies indicated that CSY bioactive nanoemulsion was effective against Gram negative organisms than Gram positive organism.

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

USDA-ARS?s Scientific Manuscript database

A biological method was used to synthesize stable silver nanoparticles. The nanoparticles were tested as larvicides against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Annona squamosa leaf broth (5%) reduced aqueous AgNO3 to stable silver nanoparticles with average particle siz...

Synthesis of silver nanoparticles using A. indicum leaf extract and their antibacterial activity.

PubMed

Ashokkumar, S; Ravi, S; Kathiravan, V; Velmurugan, S

2015-01-05

Green synthesis of silver nanoparticles has been achieved using environmentally acceptable plant extract. It is observed that Abutilon indicum leaf extract can reduce silver ions into silver nanoparticles within 15 min of reaction time. The formation and stability of the reduced silver nanoparticles in the colloidal solution were monitored by UV-Vis spectrophotometer analysis. The mean particle diameter of silver nanoparticles was calculated from the XRD pattern. FT-IR spectra of the leaf extract after the development of nanoparticles are determined to allow identification of possible functional groups responsible for the conversion of metal ions to metal nanoparticles. The AgNPs thus obtained showed highly potent antibacterial activity toward Gram-positive (Staphyloccocus aureus and Bacillus subtilis) and Gram-negative (Salmonella typhi and Escherichia coli) microorganisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Covalent attachment and growth of nanocrystalline films of photocatalytic TiOF2

NASA Astrophysics Data System (ADS)

Zhu, Jian; Lv, Fujian; Xiao, Shengxiong; Bian, Zhenfeng; Buntkowsky, Gerd; Nuckolls, Colin; Li, Hexing

2014-11-01

This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation.This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation. Electronic supplementary information (ESI) available: Methods for sample preparation, characterization and Fig. S1-S8. See DOI: 10.1039/c4nr05598e

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

NASA Astrophysics Data System (ADS)

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

2013-04-01

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.

Field-assisted synthesis of SERS-active silver nanoparticles using conducting polymers.

PubMed

Xu, Ping; Jeon, Sea-Ho; Mack, Nathan H; Doorn, Stephen K; Williams, Darrick J; Han, Xijiang; Wang, Hsing-Lin

2010-08-01

A gradient of novel silver nanostructures with widely varying sizes and morphologies is fabricated on a single conducting polyaniline-graphite (P-G) membrane with the assistance of an external electric field. It is believed that the formation of such a silver gradient is a synergetic consequence of the generation of a silver ion concentration gradient along with an electrokinetic flow of silver ions in the field-assisted model, which greatly influences the nucleation and growth mechanism of Ag particles on the P-G membrane. The produced silver dendrites, flowers and microspheres, with sharp edges, intersections and bifurcations, all present strong surface enhanced Raman spectroscopy (SERS) responses toward an organic target molecule, mercaptobenzoic acid (MBA). This facile field-assisted synthesis of Ag nanoparticles via chemical reduction presents an alternative approach to nanomaterial fabrication, which can yield a wide range of unique structures with enhanced optical properties that were previously inaccessible by other synthetic routes.

Quasi-one-dimensional arrangement of silver nanoparticles templated by cellulose microfibrils.

PubMed

Wu, Min; Kuga, Shigenori; Huang, Yong

2008-09-16

We demonstrate a simple, facile approach to the deposition of silver nanoparticles on the surface of cellulose microfibrils with a quasi-one-dimensional arrangement. The process involves the generation of aldehyde groups by oxidizing the surface of cellulose microfibrils and then the assembly of silver nanoparticles on the surface by means of the silver mirror reaction. The linear nature of the microfibrils and the relatively uniform surface chemical modification result in a uniform linear distribution of silver particles along the microfibrils. The effects of various reaction parameters, such as the reaction time for the reduction process and employed starting materials, have been investigated by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy. Additionally, the products were examined for their electric current-voltage characteristics, the results showing that these materials had an electric conductivity of approximately 5 S/cm, being different from either the oxidated cellulose or bulk silver materials by many orders of magnitude.

Green Synthesis of Silver Nanoparticles Decorated by Fe₃O₄/GO with Enhanced Catalytic Activity.

PubMed

Guo, Jian; Wang, Yu; Liu, Dan-Dan; Wan, Rong; Han, Guo-Zhi

2018-05-01

We report a simple and green approach to synthesize stable water-dispersible silver nanoparticles decorated by magnetic Fe3O4 and graphene oxide (GO). These results of UV-Vis spectra, along with TEM and SEM indicated that the water-dispersible silver nanoparticles had cluster flat structure and retained the optical properties of the original silver particle. Combining the advantages of Fe3O4 and GO, the composite nanoparticles showed enhanced catalytic activity with good recycling utilization rate by magnetic separation.

Synthesis of silver/montmorillonite nanocomposites using γ-irradiation

PubMed Central

Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Gharayebi, Yadollah; Sedaghat, Sajjad

2010-01-01

Silver nanoparticles (Ag-NPs) were synthesized into the interlamellar space of montmorillonite (MMT) by using the γ-irradiation technique in the absence of any reducing agent or heat treatment. Silver nitrate and γ-irradiation were used as the silver precursor and physical reducing agent in MMT as a solid support. The MMT was suspended in the aqueous AgNO3 solution, and after the absorption of silver ions, Ag+ was reduced using the γ-irradiation technique. The properties of Ag/MMT nanocomposites and the diameters of Ag-NPs were studied as a function of γ-irradiation doses. The interlamellar space limited particle growth (d-spacing [ds] = 1.24–1.42 nm); powder X-ray diffraction and transmission electron microscopy (TEM) measurements showed the production of face-centered cubic Ag-NPs with a mean diameter of about 21.57–30.63 nm. Scanning electron microscopy images indicated that there were structure changes between the initial MMT and Ag/MMT nanocomposites under the increased doses of γ-irradiation. Furthermore, energy dispersive X-ray fluorescence spectra for the MMT and Ag/ MMT nanocomposites confirmed the presence of elemental compounds in MMT and Ag-NPs. The results from ultraviolet-visible spectroscopy and TEM demonstrated that increasing the γ-irradiation dose enhanced the concentration of Ag-NPs. In addition, the particle size of the Ag-NPs gradually increased from 1 to 20 kGy. When the γ-irradiation dose increased from 20 to 40 kGy, the particle diameters decreased suddenly as a result of the induced fragmentation of Ag-NPs. Thus, Fourier transform infrared spectroscopy suggested that the interactions between Ag-NPs with the surface of MMT were weak due to the presence of van der Waals interactions. The synthesized Ag/MMT suspension was found to be stable over a long period of time (ie, more than 3 months) without any sign of precipitation. PMID:21170354

New insights into the formation of silver-based nanoparticles under natural and semi-natural conditions.

PubMed

Wimmer, Andreas; Kalinnik, Anna; Schuster, Michael

2018-05-10

For the first time, the natural formation of silver-based nanoparticles (Ag-b-NPs) was studied in field investigations of two pre-alpine lakes in Germany that contain geogenic silver traces in the sub-ng L -1 range. Light-sensitive microorganisms most likely accumulate and transport these silver traces from deeper water layers to the surface. At the surface of the eutrophic lake, approximately 40% of total silver (5.7 ng L -1 ) consisted of Ag-b-NPs, whereas in the oligotrophic lake with similar enrichment of silver species, no Ag-b-NPs were detected. Additional lab experiments with nature-related Ag(I) concentrations in the lower-ng L -1 range and natural organic matter with total organic carbon values of ≤5 mg L -1 revealed that, contrary to common interpretation in the literature, Ag-b-NPs are also or even preferably formed in the dark. Particle size increases gradually with increasing reaction time, showing that Ostwald ripening occurs even at such low particle concentrations. When sulfide ions are present, smaller Ag-b-NPs with a narrower size distribution are formed. Copyright © 2018 Elsevier Ltd. All rights reserved.

Colloidal silver: a novel treatment for Staphylococcus aureus biofilms?

PubMed

Goggin, Rachel; Jardeleza, Camille; Wormald, Peter-John; Vreugde, Sarah

2014-03-01

Colloidal silver is an alternative medicine consisting of silver particles suspended in water. After using this solution as a nasal spray, the symptoms of a previously recalcitrant Staphylococcus aureus (S. aureus)-infected chronic rhinosinusitis patient were observed to have improved markedly. The aim of this study was to determine whether colloidal silver has any direct bactericidal effects on these biofilms in vitro. S. aureus biofilms were grown from the ATCC 25923 reference strain on Minimum Biofilm Eradication Concentration (MBEC) device pegs, and treated with colloidal silver. Concentrations tested ranged from 10 to 150 μL colloidal silver diluted to 200 μL with sterile water in 50 μL cerebrospinal fluid (CSF) broth. Control pegs were exposed to equivalent volumes of CSF broth and sterile water. The sample size was 4 biomass values per treatment or control group. Confocal scanning laser microscopy and COMSTAT software were used to quantify biofilms 24 hours after treatment. Significant differences from control were found for all concentrations tested bar the lowest of 10 μL colloidal silver in 200 μL. At 20 μL colloidal silver, the reduction in biomass was 98.9% (mean difference between control and treatment = -4.0317 μm(3) /μm(2) , p < 0.0001). A maximum biomass reduction of 99.8% was reached at both 100 and 150 μL colloidal silver (mean differences = -4.0681 and -4.0675μm(3) /μm(2) , respectively, p < 0.0001). Colloidal silver directly attenuates in vitro S. aureus biofilms. © 2014 ARS-AAOA, LLC.

Preparation of crosslinked amphiphilic silver nanogel as thin film corrosion protective layer for steel.

PubMed

Atta, Ayman M; El-Mahdy, Gamal A; Al-Lohedan, Hamad A; Ezzat, Abdelrahman O

2014-07-17

Monodisperse silver nanoparticles were synthesized by a new developed method via reaction of AgNO3 and oleic acid with the addition of a trace amount of Fe3+ ions. Emulsion polymerization at room temperature was employed to prepare a core-shell silver nanoparticle with controllable particle size. N,N'-methylenebisacrylamide (MBA) and potassium peroxydisulfate (KPS) were used as a crosslinker, and as redox initiator system, respectively for crosslinking polymerization. The structure and morphology of the silver nanogels were characterized by Fourier transform infrared spectroscopy (FTIR), transmission and scanning electron microscopy (TEM and SEM). The effectiveness of the synthesized compounds as corrosion inhibitors for steel in 1 M HCl was investigated by various electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Monolayers of silver nanoparticle were self-assembled on the fresh active surface of the steel electrode and have been tested as a corrosion inhibitor for steel in 1 M HCl solution. The results of polarization measurements showed that nanogel particles act as a mixed type inhibitor.

Direct Coating of Nanocrystalline Diamond on Steel

NASA Astrophysics Data System (ADS)

Tsugawa, Kazuo; Kawaki, Shyunsuke; Ishihara, Masatou; Hasegawa, Masataka

2012-09-01

Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 °C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication.

New Guar Biopolymer Silver Nanocomposites for Wound Healing Applications

PubMed Central

Abdullah, Md Farooque; Das, Suvadra; Roy, Partha; Datta, Sriparna; Mukherjee, Arup

2013-01-01

Wound healing is an innate physiological response that helps restore cellular and anatomic continuity of a tissue. Selective biodegradable and biocompatible polymer materials have provided useful scaffolds for wound healing and assisted cellular messaging. In the present study, guar gum, a polymeric galactomannan, was intrinsically modified to a new cationic biopolymer guar gum alkylamine (GGAA) for wound healing applications. Biologically synthesized silver nanoparticles (Agnp) were further impregnated in GGAA for extended evaluations in punch wound models in rodents. SEM studies showed silver nanoparticles well dispersed in the new guar matrix with a particle size of ~18 nm. In wound healing experiments, faster healing and improved cosmetic appearance were observed in the new nanobiomaterial treated group compared to commercially available silver alginate cream. The total protein, DNA, and hydroxyproline contents of the wound tissues were also significantly higher in the treated group as compared with the silver alginate cream (P < 0.05). Silver nanoparticles exerted positive effects because of their antimicrobial properties. The nanobiomaterial was observed to promote wound closure by inducing proliferation and migration of the keratinocytes at the wound site. The derivatized guar gum matrix additionally provided a hydrated surface necessary for cell proliferation. PMID:24175306

New guar biopolymer silver nanocomposites for wound healing applications.

PubMed

Ghosh Auddy, Runa; Abdullah, Md Farooque; Das, Suvadra; Roy, Partha; Datta, Sriparna; Mukherjee, Arup

2013-01-01

Wound healing is an innate physiological response that helps restore cellular and anatomic continuity of a tissue. Selective biodegradable and biocompatible polymer materials have provided useful scaffolds for wound healing and assisted cellular messaging. In the present study, guar gum, a polymeric galactomannan, was intrinsically modified to a new cationic biopolymer guar gum alkylamine (GGAA) for wound healing applications. Biologically synthesized silver nanoparticles (Agnp) were further impregnated in GGAA for extended evaluations in punch wound models in rodents. SEM studies showed silver nanoparticles well dispersed in the new guar matrix with a particle size of ~18 nm. In wound healing experiments, faster healing and improved cosmetic appearance were observed in the new nanobiomaterial treated group compared to commercially available silver alginate cream. The total protein, DNA, and hydroxyproline contents of the wound tissues were also significantly higher in the treated group as compared with the silver alginate cream (P < 0.05). Silver nanoparticles exerted positive effects because of their antimicrobial properties. The nanobiomaterial was observed to promote wound closure by inducing proliferation and migration of the keratinocytes at the wound site. The derivatized guar gum matrix additionally provided a hydrated surface necessary for cell proliferation.

Green synthesis of silver nanoparticles using green tea leaves: Experimental study on the morphological, rheological and antibacterial behaviour

NASA Astrophysics Data System (ADS)

Nakhjavani, Maryam; Nikkhah, V.; Sarafraz, M. M.; Shoja, Saeed; Sarafraz, Marzieh

2017-10-01

In this paper, silver nanoparticles are produced via green synthesis method using green tea leaves. The introduced method is cost-effective and available, which provides condition to manipulate and control the average nanoparticle size. The produced particles were characterized using x-ray diffraction, scanning electron microscopic images, UV visualization, digital light scattering, zeta potential measurement and thermal conductivity measurement. Results demonstrated that the produced samples of silver nanoparticles are pure in structure (based on the x-ray diffraction test), almost identical in terms of morphology (spherical and to some extent cubic) and show longer stability when dispersed in deionized water. The UV-visualization showed a peak in 450 nm, which is in accordance with the previous studies reported in the literature. Results also showed that small particles have higher thermal and antimicrobial performance. As green tea leaves are used for extracting the silver nanoparticles, the method is eco-friendly. The thermal behaviour of silver nanoparticle was also analysed by dispersing the nanoparticles inside the deionized water. Results showed that thermal conductivity of the silver nano-fluid is higher than that of obtained for the deionized water. Activity of Ag nanoparticles against some bacteria was also examined to find the suitable antibacterial application for the produced particles.

Some advances in the silver physical development of latent prints on paper

NASA Astrophysics Data System (ADS)

Cantu, Antonio A.; Leben, Deborah A.; Wilson, Kelley

2003-09-01

Silver physical development, a now-abandoned technique used for developing photographic film or paper, is one of the most powerful methods for visualizing latent prints on paper. The method develops the water-insoluble components in the print residue. These components include the "fats and oils" or lipids found on the skin of fingers. The resulting developed print, referred to as a silver physically developed (Ag-PD) print, is made up of (gray to black) silver particles adhered to the fingerprint residue. Such prints are usually intensified (made darker) with a hypochlorite treatment. This process converts silver to silver oxide making the Ag-PD print become a Ag2O-PD prints. Often such (Ag-PD or Ag2O-PD) prints are found on areas with heavy or patterned printing making them difficult to see. This work resolves this problem by chemically lightening the print and darkening (suppressing) the interfering background.

Exploration of Phyllanthus acidus mediated silver nanoparticles and its activity against infectious bacterial pathogen.

PubMed

Sowmya, Cherukuri; Lavakumar, Vuppalapati; Venkateshan, Narayanan; Ravichandiran, Velayutham; Saigopal, D V R

2018-04-20

In our present investigation, synthesis of nontoxic, eco friendly and cost effective silver nanoparticles, Phyllanthus acidus (P. acidus) was used as starting material. The influence of phyto-constituents present in aqueous extracts of Phyllanthus acidus was found to be effective in reduction of silver nitrate to free silver nanoparticles (PA-AgNPs). HPTLC finger print analysis reveals the presence of flavonoid, quercetin in aqueous extracts of Phyllanthus acidus. Surface plasmon racemonance exhibited λ max at 462 nm through UV-Vis spectroscopy. Zeta size revealed that the size of nanoparticles were with in the range of 65-250 nm with polydisperse index (PDI) of 0.451. The negative charge of zeta potential value (- 16.4) indicates repulsion among PA-AgNPs with their excellent stability. FESEM-EDAX, XRD and TEM analysis confirmed the presence of nano-crystalline PA-AgNPs with different morphological textures. Further, PA-AgNPs has shown potent antibacterial effect on E. coli cells. The greater antibacterial effect (viable and dead cells) of PA-AgNPs were confirmed by using acridine orange (AO) dye which can able to provide insight of healthy as well as damaged DNA. Live cells emit florescence green and dead cells (treated with PA-AgNPS at 20 and 40 µg/ml) appear as pale orange red colour. Post treatment, investigations of PA-AgNPs on E. coli cells under SEM was found to be effective against cell membrane damages which leads to cell death or cell growth arrest. Hence, from the above findings, we strongly recommend silver nanoparticles from Phyllanthus acidus can be used as a potential source for antimicrobial agent for chronic infections and also against other harmful microorganisms.

Silver Nanopartilces After Zebrafish Development and Larval Behavior: Distinct Roles for Particle Size, Coating and Composition

EPA Science Inventory

Background: Silver nanoparticles (AgNPs) act as antibacterials by releasing monovalent silver (Ag+) and are increasingly used in consumer products, thus elevating exposures in human and environmental populations. In vitro models indicate that AgNPs are likely to be developmental ...

Gold particle formation via photoenhanced deposition on lithium niobate

NASA Astrophysics Data System (ADS)

Zaniewski, A. M.; Meeks, V.; Nemanich, R. J.

2017-05-01

In this work, we report on a technique to reduce gold chloride into sub-micron particles and nanoparticles. We use photoelectron transfer from periodically polarized lithium niobate (PPLN) illuminated with above band gap light to drive the surface reactions required for the reduction and particle formation. The particle sizes and distributions on the PPLN surface are sensitive to the solution concentration, with inhibited nucleation and large particles (>150 nm) for both low (2E-8M to 9E-7M) and high (1E-5M to 1E-3M) concentrations of gold chloride. At midrange values of the concentration, nucleation is more frequent, resulting in smaller sized particles (<150 nm). We compare the deposition process to that for silver, which has been previously studied. We find that the reduction of gold chloride into nanoparticles is inhibited compared to silver ion reduction, due to the multi-step reaction required for gold particle formation. This also has consequences for the resulting deposition patterns: while silver deposits into nanowires along boundaries between areas with opposite signed polarizations, such patterning of the deposition is not observed for gold, for a wide range of concentrations studied (2E-8 to 1E-3M).

Bulk Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

DTIC Science & Technology

2014-05-13

nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and...the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta...approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are

Electrode characteristics of nanocrystalline AB{sub 5} compounds prepared by mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Z.; Chen, Z.; Zhou, D.

1998-10-01

Nanocrystalline LaNi{sub 5} and LaNi{sub 4.5}Si{sub 0.5} synthesized by mechanical alloying were used as negative materials for Ni-MH batteries. It was found that the electrodes prepared with the nanocrystalline powders had similar discharge capacities, better activation behaviors, and longer cycle lifetimes, compared with the negative electrode prepared with polycrystalline coarse-grained LaNi{sub 5} alloy. The properties of the electrodes prepared with these nanocrystalline materials were attributed to the structural characteristics of the compounds caused by mechanical alloying.

Synthesis of nanocrystalline ZnO thin films by electron beam evaporation

NASA Astrophysics Data System (ADS)

Kondkar, V.; Rukade, D.; Bhattacharyya, V.

2018-05-01

Nanocrystalline ZnO thin films have potential for applications in variety of optoelectronic devices. In the present study, nanocrystalline thin films of ZnO are grown on fused silica substrate using electron beam (e-beam) evaporation technique. Phase identification is carried out using Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy. Ultraviolet-Visible (UV-Vis) spectroscopic analysis is carried out to calculate energy band gap of the ZnO film. Surface morphology of the film is investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Highly quality nanocrystalline thin films of hexagonal wurtzite ZnO are synthesized using e-beam evaporation technique.

The mechanism of the photochemical oxidation of water to oxygen with silver chloride colloids

NASA Astrophysics Data System (ADS)

Chandrasekaran, K.; Thomas, J. K.

1983-05-01

Photoexcitation of silver chloride colloids in the presence of excess silver ions, leads to the decomposition of water. Hydroxyl radicals were found to be intermediates in the decomposition process. Irradiation leads to hydroxyl radicals, which recombine to give hydrogen peroxide, on the colloidal particle surface. Subsequent decomposition of H 2O 2 to give O 2 is catalyzed by silver ions. Addition of alcohols such as methanol and isopropanol reduce the oxygen yield, as they react with OH radicals and reduce the H 2O 2 yield.

Silver nanoparticles: in vivo toxicity in zebrafish embryos and a comparison to silver nitrate

NASA Astrophysics Data System (ADS)

Mosselhy, Dina A.; He, Wei; Li, Dan; Meng, Yaping; Feng, Qingling

2016-08-01

The wide antimicrobial administration of silver nanoparticles (AgNPs) has raised the risks associated with their exposure. However, there is lack of robust toxicological data for the applied AgNPs to be in line with their wide antimicrobial applications. This study therefore set out to assess the in vivo toxicity of two different sizes of AgNPs using zebrafish embryos ( Danio rerio) as a brilliant in vivo model. The pivotal role of size of AgNPs in the toxicity was highlighted, wherein the smaller AgNPs (Ag-9 nm) exhibited more embryo toxicities than the larger particles (Ag-30 nm). Much uncertainty still exists about whether the cause of in vivo toxicity of AgNPs is the physicochemical properties of AgNPs or the released silver ions (Ag+). Therefore, another purpose of this study is to compare the toxicity of AgNPs with silver nitrate (AgNO3) in terms of mortality, hatchability and cardiac rates, and a series of phenotypic endpoints of zebrafish embryos. Collectively, the present results point towards the remarkable size-dependent toxicity of AgNPs. Wherein, the smaller AgNPs (9 ± 2 nm) induce increased mortality rates and decreased hatchability rates than the larger particles (30 ± 5 nm) in a dose-dependent manner. Besides, AgNPs and AgNO3 induce holistic different toxic mortality and hatchability rates. We have also found striking discrepancies in the phenotypic defects that were induced by AgNPs and AgNO3. The significant phenotypic defect induced by AgNPs is the axial deformity, while it is the deposition of Ag+ on the embryonic chorion for AgNO3. Therefore, it is proposed that AgNPs and AgNO3 induce different in vivo toxicities.

Green Route for Silver Nanoparticles Synthesis by Raphanus Sativus Extract in a Continuous Flow Tubular Microreactor

NASA Astrophysics Data System (ADS)

Jolhe, P. D.; Bhanvase, B. A.; Patil, V. S.; Sonawane, S. H.

The present work deals with the investigation of the greener route for the production of silver nanoparticles using Raphanus sativus (R. sativus) bioextract in a continuous flow tubular microreactor. The parameters affecting the particle size and distribution were investigated. From the results obtained it can be inferred that the ascorbic acid (reducing agent) present in the R. sativus bioextract is responsible for the reduction of silver ions. At optimum condition, the particle size distribution of nanoparticles is found between 18nm and 39nm. The absorbance value was found to be decreased with an increase in the diameter of the microreactor. It indicates that a number of nuclei are formed in the micrometer sized (diameter) reactor because of the better solute transfer rate leading to the formation of large number of silver nanoparticles. The study of antibacterial activity of green synthesized silver nanoparticles shows effective inhibitory activity against waterborne pathogens, Shegella and Listeria bacteria.

Effect of mechanical alloying and heat treatment on the behavior of fe - 28% al - 5% cr powder with nanocrystalline structure

NASA Astrophysics Data System (ADS)

Tang, W. M.; Liu, H. L.; Wang, Y. X.; Xu, G. O.; Zheng, Z. X.

2012-05-01

Nanocrystalline powders of alloy Fe - 28% Al - 5% Cr (at.%) obtained by mechanical alloying from powdered iron, aluminum, and preliminarily alloyed Fe - 20% Cr are studied. The chemical composition is shown to be homogenized. The changes in the structure and in the morphology of the particles in the process of ball milling and subsequent heat treatment are determined. The alloying is shown to occur by the mechanism of continuous diffusion mixing.

Structural characterization and antimicrobial properties of silver nanoparticles prepared by inverse microemulsion method.

PubMed

Wani, Irshad A; Khatoon, Sarvari; Ganguly, Aparna; Ahmed, Jahangeer; Ahmad, Tokeer; Manzoor, Nikhat

2013-01-01

Silver nanoparticles have been synthesized in the inverse microemulsions formed using three different surfactants viz., cetyl-trimethyl ammonium bromide (CTAB), Tergitol and Triton X-100. We have done a systematic study of the effect of the surfactants on the particle size and properties of the silver nanoparticles. Microscopic studies show the formation of spheres, cubes and discs shaped silver nanostructures with the size in the range from 8 to 40 nm. Surface plasmon resonance (SPR) peak was observed around 400 nm and 500 nm. In addition to SPR some extra peaks have also been observed due to the formation of silver metal clusters. The surface area increases from 3.45 to 15.06 m(2)/g with decreasing the size of silver nanoparticles (40-8 nm). To investigate the antimicrobial activity of silver nanoparticles, the nanoparticles were tested against the yeast, Candida albicans and the bacterium, E. coli. The results suggest very good antimicrobial activity of the silver nanoparticles against the test microbes. The mode of action of the antimicrobial activity was also proposed. Copyright © 2012 Elsevier B.V. All rights reserved.

Antibacterial activity and toxicity of silver - nanosilver versus ionic silver

NASA Astrophysics Data System (ADS)

Kvitek, L.; Panacek, A.; Prucek, R.; Soukupova, J.; Vanickova, M.; Kolar, M.; Zboril, R.

2011-07-01

The in vitro study of antibacterial activity of silver nanoparticles (NPs), prepared via modified Tollens process, revealed high antibacterial activity even at very low concentrations around several units of mg/L. These concentrations are comparable with concentrations of ionic silver revealing same antibacterial effect. However, such low concentrations of silver NPs did not show acute cytotoxicity to mammalian cells - this occurs at concentrations higher than 60 mg/L of silver, while the cytotoxic level of ionic silver is much more lower (approx. 1 mg/L). Moreover, the silver NPs exhibit lower acute ecotoxicity against the eukaryotic organisms such as Paramecium caudatum, Monoraphidium sp. and D. melanogaster. The silver NPs are toxic to these organisms at the concentrations higher than 30 mg/L of silver. On contrary, ionic silver retains its cytoxicity and ecotoxicity even at the concentration equal to 1 mg/L. The performed experiments demonstrate significantly lower toxicity of silver NPs against the eukaryotic organisms than against the prokaryotic organisms.

Printed silver nanowire antennas with low signal loss at high-frequency radio

NASA Astrophysics Data System (ADS)

Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

2012-05-01

Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those

Cyanidation Study of Slag Rich in Silver

NASA Astrophysics Data System (ADS)

Pérez-Labra, Miguel; Romero-Serrano, J. Antonio; Ávila-Davila, E. O.; Reyes-Pérez, M.; Barrientos-Hernández, F. R.; Hernández, I. A. Lira

Slag from smelting reduction processes were characterized by chemical analysis, XRD, SEM-EDS and XRF. The results revealed Ag concentrations of 362 g/t of slag, the slag mineralogical characterization by XRD and SEM-EDS showed mineralogical species oxidized complex containing Pb, Zn, Ca, Si, Fe, As, S in its structure, silver was found in globules associated lead in the slag and the furutobeite specie. The leaching study was conducted to evaluate process variables such as NaCN concentration: from 7.8×10-3M - 1.26×10-1M, temperature: 25-50°C, particle size: +140 mesh to -400 mesh, stirring speed of 750 rpm - 900 rpm. All studies were performed with a NaOH concentration of 0.2 M. The optimal values of silver recovery encountered in conditions of 7.8×10-3M NaCN, agitation rate of 750 rpm, temperature of 35°C and with a treatment time of 240 min. We also observed that a particle size -400 mesh will have optimum recoveries compared to +140 mesh, +200, +270 and +325.

In situ loading of well-dispersed silver nanoparticles on nanocrystalline magnesium oxide for real-time monitoring of catalytic reactions by surface enhanced Raman spectroscopy.

PubMed

Zhang, Kaige; Li, Gongke; Hu, Yuling

2015-10-28

The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn(2+) linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real-time monitoring of the catalytic reaction process of 4-nitrothiophenol to 4-aminothiophenol in an aqueous medium by observing the SERS signals of the reactant, intermediate and final products. The intrinsic reaction kinetics and reaction mechanism of this reaction were also investigated. This SERS-based synergy technique provides a novel approach for quantitative in situ monitoring of catalytic chemical reaction processes.

"Bulk" Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

NASA Astrophysics Data System (ADS)

Tschopp, M. A.; Murdoch, H. A.; Kecskes, L. J.; Darling, K. A.

2014-06-01

It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

A novel polyol method to synthesize colloidal silver nanoparticles by ultrasonic irradiation.

PubMed

Byeon, Jeong Hoon; Kim, Young-Woo

2012-01-01

A polyol synthesis of silver nanoparticles in the presence of ultrasonic irradiation was compared with other configurations (at ambient temperature, 120° C, and 120 °C with injected solutions) in the absence of ultrasonic irradiation in order to obtain systematic results for morphology and size distribution. For applying ultrasonic irradiation, rather fine and uniform spherical silver particles (21±3.7 nm) were obtained in a simple (at ambient temperature without mechanical stirring) and fast (within 4 min, 3.61×10(-3) mol min(-1)) manner than other cases (at ambient temperature (for 8 h, 0.03×10(-3) mol min(-1)): 86±16.8 nm, 120 °C (for 12 min, 1.16×10(-3) mol min(-1)): 64±14.9 nm, and 120 °C with injected solutions (during 12 min): 35±6.8 nm; all other cases contained anisotropic shaped particles). Even though the temperature of polyol reaction reached only at 80 °C (<120 °C) in the presence of ultrasonic irradiation, a uniform mixing (i.e. enhanced collision between silver particle and surrounding components) by ultrasonic irradiation might induce a better formation kinetics and morphological uniformity. Copyright © 2011 Elsevier B.V. All rights reserved.

Heteroaggregation of Silver Nanoparticles with Clay Minerals in Aqueous System

NASA Astrophysics Data System (ADS)

Liu, J.; Burrow, E.; Hwang, Y.; Lenhart, J.

2013-12-01

Nanoparticles are increasingly being used in industrial processes and consumer products that exploit their beneficial properties and improve our daily lives. Nevertheless, they also attract attention when released into natural environment due to their potential for causing adverse effects. The fate and transport of nanoparticles in aqueous systems have been the focus of intense study. However, their interactions with other natural particles have received only limited attention. Clay minerals are ubiquitous in most aquatic systems and their variably charged surfaces can act as deposition sites that can alter the fate and transport of nanoparticles in natural aqueous environments. In this study, we investigated the homoaggregation of silver nanoparticles with different coating layers and their heteroaggregation behavior with clay minerals (illite, kaolinite, montmorillonite) in neutral pH solutions. Silver nanoparticles with a nominal diameter of 80 nm were synthesized with three different surface coating layers: uncoated, citrate-coated and Tween-coated. Illite (IMt-2), kaolinite (KGa-2), and montmorillonite (SWy-2) were purchased from the Clay Mineral Society (Indiana) and pretreated to obtain monocationic (Na-clay) and dicationic (Ca-clay) suspensions before the experiments. The change in hydrodynamic diameter as a function of time was monitored using dynamic light scattering (DLS) measurements in order to evaluate early stage aggregation as a function of electrolyte concentration in both the homo- and heteroaggregation scenarios. A shift in the critical coagulation concentration (CCC) values to lower electrolyte concentrations was observed in binary systems, compared to single silver nanoparticle and clay systems. The results also suggest more rapid aggregation in binary system during the early aggregation stage when compared to the single-particle systems. The behavior of citrate-coated silver nanoparticles was similar to that of the bare particles, while the

An investigation on the preparation of nanocrystalline hydrous zirconia from zirconium tungstate

NASA Astrophysics Data System (ADS)

Antunes, M.; Perottoni, C. A.; Gouvêa, D.; Machado, G.; Zorzi, J. E.

2018-02-01

Hydrous nanocrystalline zirconia was prepared from an unusual precursor—the bimetallic oxide zirconium tungstate (ZrW2O8)—in alkaline medium. Different experimental conditions (NaOH concentration, time and temperature) were used to investigate the effects on crystallographic, morphological, chemical and thermal characteristics of the products. The resulting materials are composed of particles with a crystal structure similar to that of cubic ZrO2 (or a mixture of tetragonal and cubic phases, depending on the synthesis conditions), with particle size around 5 nm and crystallites around 3 nm in diameter. These particles form high surface area agglomerates, exhibiting mesoporosity and capacity for adsorption of water and carbon dioxide. The synthesis mechanism appears to be constituted, first, by a chemical substitution reaction between the WO4 tetrahedra and hydroxyl ions, with subsequent solubilization of the structure. Indeed, excess hydroxyls in the medium form colloidal zirconium ions which polymerize/condense, generating crystalline nuclei in a process facilitated by heterogeneous nucleation and supersaturation. The presence of residual tungsten in all samples appears to be a key element for stabilizing the size and crystalline structure of the materials produced.

Biocatalytic and antibacterial visualization of green synthesized silver nanoparticles using Hemidesmus indicus.

PubMed

Latha, M; Sumathi, M; Manikandan, R; Arumugam, A; Prabhu, N M

2015-05-01

In the present investigation, we described the green synthesis of silver nanoparticles using plant leaf extract of Hemidesmus indicus. The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). TEM images proved that the synthesized silver nanoparticles were spherical in shape with an average particle size of 25.24 nm. To evaluate antibacterial efficacy, bacteria was isolated from poultry gut and subjected to 16S rRNA characterization and confirmed as Shigella sonnei. The in vitro antibacterial efficacy of synthesized silver nanoparticles was studied by agar bioassay, well diffusion and confocal laser scanning microscopy (CLSM) assay. The H. indicus mediated synthesis of silver nanoparticles shows rapid synthesis and higher inhibitory activity (34 ± 0.2 mm) against isolated bacteria S. sonnei at 40 μg/ml. Copyright © 2015 Elsevier Ltd. All rights reserved.

Hydroxy propyl cellulose capped silver nanoparticles produced by simple dialysis process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francis, L.; Balakrishnan, A.; Sanosh, K.P.

2010-08-15

Silver (Ag) nanoparticles ({approx}6 nm) were synthesized using a novel dialysis process. Silver nitrate was used as a starting precursor, ethylene glycol as solvent and hydroxy propyl cellulose (HPC) introduced as a capping agent. Different batches of reaction mixtures were prepared with different concentrations of silver nitrate (AgNO{sub 3}). After the reduction and aging, these solutions were subjected to ultra-violet visible spectroscopy (UVS). Optimized solution, containing 250 mg AgNO{sub 3} revealed strong plasmon resonance peak at {approx}410 nm in the spectrum indicating good colloidal state of Ag nanoparticles in the diluted solution. The optimized solution was subjected to dialysis processmore » to remove any unreacted solvent. UVS of the optimized solution after dialysis showed the plasmon resonance peak shifting to {approx}440 nm indicating the reduction of Ag ions into zero-valent Ag. This solution was dried at 80 {sup o}C and the resultant HPC capped Ag (HPC/Ag) nanoparticles were studied using transmission electron microscopy (TEM) for their particle size and morphology. The particle size distribution (PSD) analysis of these nanoparticles showed skewed distribution plot with particle size ranging from 3 to 18 nm. The nanoparticles were characterized for phase composition using X-ray diffractrometry (XRD) and Fourier transform infrared spectroscopy (FT-IR).« less

Structural, optical and photo-catalytic activity of nanocrystalline NiO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Ghamdi, Attieh A.; Abdel-wahab, M. Sh., E-mail: mshabaan90@yahoo.com; Materials Science and Nanotechnology Department, Faculty of Postgraduate Studies for Advanced Sciences, Beni-Suef University, Beni-Suef

2016-03-15

Highlights: • Synthesis of nanocrystalline NiO thin films with different thicknesses using DC magnetron sputtering technique. • Effect of film thickness and particle size on photo-catalytic degradation of methyl green dye under UV light was studied. • The deposited NiO thin films are efficient, stable and possess high photo-catalytic activity upon reuse. - Abstract: Physical deposition of nanocrystalline nickel oxide (NiO) thin films with different thickness 30, 50 and 80 nm have been done on glass substrate by DC magnetron sputtering technique and varying the deposition time from 600, 900 to 1200 s. The results of surface morphology and opticalmore » characterization of these films obtained using different characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), photoluminescence (PL) and UV–vis spectrophotometry provide important information like formation of distinct nanostructures in different films and its effect on their optical band gap which has decreased from 3.74 to 3.37 eV as the film thickness increases. Most importantly these films have shown very high stability and a specialty to be recycled without much loss of their photo-catalytic activity, when tested as photo-catalysts for the degradation of methyl green dye (MG) from the wastewater under the exposure of 18 W energy of UV lamp.« less

Growth characteristics of nanocrystalline silicon films fabricated by using chlorinated precursors at low temperatures.

PubMed

Huang, Rui; Ding, Honglin; Song, Jie; Guo, Yanqing; Wang, Xiang; Lin, Xuanying

2010-11-01

We employed plasma enhanced chemical vapor deposition technique to fabricate nanocrystalline Si films at a low temperature of 250 degrees C by using SiCl4 and H2 as source gases. The evolution of microstructure of the films with deposition periods shows that nanocrystalline Si can be directly grown on amorphous substrate at the initial growth process, which is in contrast to the growth behavior observed in the SiH4/H2 system. Furthermore, it is interesting to find that the area density of nanocrystalline Si as well as grain size can be controlled by modulating the concentration of SiCl4. By decreasing the SiCl4 concentration, the area density of nanocrystalline Si can be enhanced up to 10(11) cm(-2), while the grain size is shown to decrease down to 10 nm. It is suggested that Cl plays an important role in the low-temperature growth of nanocrystalline Si.

Silver-tin alloys and amalgams: electrochemical considerations.

PubMed

Mueller, H J

1980-01-01

The corrosion potential and anodic polarization profiles of a representative number of silver-tin alloys and their corresponding amalgams in a physiological solution were determined and compared to their microstructures. For the alloys with tin-content greater than 27%(wt) and for all amalgams, the corrosion process is related to the attack of free tin for the alloys and to the gamma-2 tin for the amalgams. The gamma-2 concentration in the amalgams increases with an increase in tin-content. For alloys with tin-content less than 27%, the corrosion process is even more restricted than for the process observed with pure silver. From a developed theory based upon the potential-time and polarization results, association of the O2 reduction process on a SnO cathodic film to an intermediate specie of H2O2 is made. The rate of H2O2 decomposition on a SnO surface in a four electron process is thought to control the O2 reduction overvoltage. The O2 reduction overvoltage decreases with increases in the silver-content of the amalgam, particularily seen with the 8 and 12% tin compositions. Due to the polarization induced corrosion process, a phase with high silver and high mercury concentrations was observed over the unreacted particles.

Grain Size Threshold for Enhanced Irradiation Resistance in Nanocrystalline and Ultrafine Tungsten

DOE PAGES

El Atwani, Osman; Hinks, Jonathan; Greaves, Graeme; ...

2017-02-21

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess ~10–20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency.

Fluorescence Quenching of Humic Acid by Coated Metallic Silver Particles.

PubMed

Zhu, Guocheng; Yin, Jun

2017-07-01

Natural organic matter is an important component of the aquatic environments, which has attracted wide attention to its influence of interaction with other pollutants. The present work aimed to investigate its fluorescence quenching (FQ) by coated metallic silver particles (AgNPs). In this work, using fluorescence spectroscopy in conjunction with UV-Vis spectroscopy and dynamic light scattering, the effect of coated AgNPs on fluorescence quenching intensity (FQI) of humic acid (HA) was assessed. In addition, the influence of electrolytes (NaCl, NaNO 3 and CaNO 3 ) in the FQI was observed. Results showed that with AgNPs dosage increased (>1.17X10 -3  mM), fluorescence quantum yield of HA gradually decreased, which implies that the FQ occurred. Furher observation showed that the FQ process followed both first-order and second-order Stern-Volmer functions. The FQ process was affected by the electrolytes: NaCl had an effect on reduction of FQI, possibly resulting from dissolution of AgNPs; Both of NaNO 3 and Ca(NO 3 ) 2 had an effect on the FQ of HA but Ca(NO 3 ) 2 presented greater degree. As a result, the FQ degree of HA by alone electrolyte was listed in descent order as Ca(NO 3 ) 2  > NaNO 3  > NaCl, which also implies the subsequent experimental results, indicating the FQ degree of HA by mutual electrolytes as Ca(NO 3 ) 2  + NaNO 3  > Ca(NO 3 ) 2  + NaCl > NaNO 3  + NaCl.

Collective behavior of silver plasma during pulsed laser ablation

NASA Astrophysics Data System (ADS)

Dildar, I. M.; Rehman, S.; Khaleeq-ur-Rahman, M.; Bhatti, K. A.; Shuaib, A.

2015-07-01

The present work reports an electrical investigation of silver plasma using a self-fabricated Langmuir probe in air and under a low vacuum (~10-3 torr). A silver target was irradiated with a Q-switched Nd:YAG laser with the wavelength 1.064 µm, energy 10 mJ, pulse duration 9-14 ns and power 1.1 MW. The collective behavior of a silver plasma plume is studied using a Langmuir probe as an electrical diagnostic technique. By applying different positive and negative voltages to the probe, the respective signals are collected on a four channels digital storage oscilloscope having a frequency of 500 MHz. An I-V curve helps to measure electron temperature and electron density directly and plasma frequency, response time, Debye length and number of particles in ‘Debye’s sphere’ indirectly using the theory of Langmuir probe and mathematical formulas. The floating potential is measured as negative for laser induced silver plasma in air and vacuum, following the theory of plasma.

Reactive Ball Milling to Fabricate Nanocrystalline Titanium Nitride Powders and Their Subsequent Consolidation Using SPS

NASA Astrophysics Data System (ADS)

El-Eskandarany, M. Sherif

2017-05-01

The room-temperature reactive ball milling (RBM) approach was employed to synthesize nanostructured fcc-titanium nitride (TiN) powders, starting from milling hcp-titanium (Ti) powders under 10 bar of a nitrogen gas atmosphere, using a roller mill. During the first and intermediate stage of milling, the agglomerated Ti powders were continuously disintegrated into smaller particles with fresh surfaces. Increasing the RBM time led to an increase in the active-fresh surfaces of Ti, resulting increasing of the mole fraction of TiN against unreacted hcp-Ti. Toward the end of the RBM time (20 h), ultrafine spherical powder (with particles 0.5 μm in diameter) of the fcc-TiN phase was obtained, composed of nanocrystalline grains with an average diameter of 8 nm. The samples obtained after different stages of RBM time were consolidated under vacuum at 1600 °C into cylindrical bulk compacts of 20 mm diameter, using spark plasma sintering technique. These compacts that maintained their nanocrystalline characteristics with an average grain size of 56 nm in diameter, possessed high relative density (above 99% of the theoretical density). The Vickers hardness of the as-consolidated TiN was measured and found to be 22.9 GPa. The modulus of elasticity and shear modulus of bulk TiN were measured by a nondestructive test and found to be 384 and 189 GPa, respectively. In addition, the coefficient of friction of the end-product TiN bulk sample was measured and found to be 0.35.

Malva parviflora extract assisted green synthesis of silver nanoparticles

NASA Astrophysics Data System (ADS)

Zayed, Mervat F.; Eisa, Wael H.; Shabaka, A. A.

2012-12-01

Five plant leaf extracts (Malva parviflora, Beta vulgaris subsp. Vulgaris, Anethum graveolens, Allium kurrat and Capsicum frutescens) were screened for their bioreduction behavior for synthesis of silver nanoparticles. M. parviflora (Malvaceae) was found to exhibit the best reducing and protecting action in terms of synthesis rate and monodispersity of the prepared silver nanoparticles. Our measurements indicate that biosynthesis of Ag nanoparticles by M. parviflora produces Ag nanoparticles with the diameters in the range of 19-25 nm. XRD studies reveal a high degree of crystallinity and monophasic Ag nanoparticles of face-centered cubic structure. FTIR analysis proved that particles are reduced and stabilized in solution by the capping agent that is likely to be proteins secreted by the biomass. The present process is an excellent candidate for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive.

Aspartame-stabilized gold-silver bimetallic biocompatible nanostructures with plasmonic photothermal properties, antibacterial activity, and long-term stability.

PubMed

Fasciani, Chiara; Silvero, M Jazmin; Anghel, Maria Alexandra; Argüello, Gerardo A; Becerra, Maria Cecilia; Scaiano, Juan C

2014-12-17

Gold-silver core-shell nanoparticles stabilized with a common sweetener, aspartame (AuNP@Ag@Asm), combine the antimicrobial properties of silver with the photoinduced plasmon-mediated photothermal effects of gold. The particles were tested with several bacterial strains, while biocompatibility was verified with human dermal fibroblasts.

A Nanocrystalline Fe2O3 Film Anode Prepared by Pulsed Laser Deposition for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Teng, Xiaoling; Qin, Youzhi; Wang, Xia; Li, Hongsen; Shang, Xiantao; Fan, Shuting; Li, Qiang; Xu, Jie; Cao, Derang; Li, Shandong

2018-02-01

Nanocrystalline Fe2O3 thin films are deposited directly on the conduct substrates by pulsed laser deposition as anode materials for lithium-ion batteries. We demonstrate the well-designed Fe2O3 film electrodes are capable of excellent high-rate performance (510 mAh g- 1 at high current density of 15,000 mA g- 1) and superior cycling stability (905 mAh g- 1 at 100 mA g- 1 after 200 cycles), which are among the best reported state-of-the-art Fe2O3 anode materials. The outstanding lithium storage performances of the as-synthesized nanocrystalline Fe2O3 film are attributed to the advanced nanostructured architecture, which not only provides fast kinetics by the shortened lithium-ion diffusion lengths but also prolongs cycling life by preventing nanosized Fe2O3 particle agglomeration. The electrochemical performance results suggest that this novel Fe2O3 thin film is a promising anode material for all-solid-state thin film batteries.

Moderating effect of ammonia on particle growth and stability of quasi-monodisperse silver nanoparticles synthesized by the Turkevich method.

PubMed

Gorup, Luiz F; Longo, Elson; Leite, Edson R; Camargo, Emerson R

2011-08-15

A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90 °C. After approximately 12 min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6 nm after 17 min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy. Copyright © 2011 Elsevier Inc. All rights reserved.

Nanocrystalline copper films are never flat.

PubMed

Zhang, Xiaopu; Han, Jian; Plombon, John J; Sutton, Adrian P; Srolovitz, David J; Boland, John J

2017-07-28

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Thermal conductivity enhancement of nano-silver particles dispersed ethylene glycol based nanofluids

NASA Astrophysics Data System (ADS)

Khamliche, Touria; Khamlich, Saleh; Doyle, Terry B.; Makinde, Daniel; Maaza, Malik

2018-03-01

This contribution reports on the thermal conductivity enhancement of nano-silver particles (nAgPs) based nanofluids with various nAgPs’ shapes in view of their potential application in concentrated solar power systems. More accurately, the thermal conductivity behaviour of suspensions of nAgPs dispersed ethylene glycol (nAgPs:EG), prepared by a simple and cost effective chemical synthesis method, is compared with a theoretical prediction. The effect of aging time on the shape of the dispersed nAgPs was clearly observed by the structural, optical and morphological analysis. Spherically shaped and Ag nanowires (AgNWs) with high yields were observed when the nAgPs was aged for 1 and 5 h, respectively. The observed AgNWs showed high aspect ratio (≥200) when EG and polyvinylpyrrolidone (PVP) were used as reductant and structure-directing agents. The thermal conductivity measurements on nAgPs:EG nanofuids with different volume fractions of nAgPs were conducted in a temperature range 25 < T < 50 °C using a guarded hot plate (GHP) method. The thermal conductivity manifested a generally monotonic increase with temperature and an approximately linear relationship with the volume fraction of the nAgPs. Particularly, an enhancement of up to 23% was observed when the nanofluid was aged for 5 h and AgNWs were dominant.

Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

NASA Astrophysics Data System (ADS)

Jakubowicz, J.; Adamek, G.; Sopata, M.; Koper, J. K.; Siwak, P.

2017-12-01

The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

PubMed Central

Jeong, Lim; Park, Won Ho

2014-01-01

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

Fabrication of nano-silver particles using Cymodocea serrulata and its cytotoxicity effect against human lung cancer A549 cells line

NASA Astrophysics Data System (ADS)

Palaniappan, P.; Sathishkumar, G.; Sankar, R.

2015-03-01

The present study reports, green synthesis of bioactive silver nanoparticles (AgNPs) under different temperature (60 °C, room temperature and 4° refrigerator) using the aqueous extract of sea grass Cymodocea serrulata as a potential bioreductant. Increased temperature fabricates more AgNPs compare to room temperature and refrigerator condition. At first the reduction of Ag+ ions were confirmed through color change which produces an absorbance spectra at 420 nm in UV-Visible spectrophotometer. Additionally various exclusive instrumentations such as X-ray diffraction (XRD), Dynamic light scattering (DLS), scanning electron microscope (SEM) analysis and Transmission electron microscope (TEM) were authorizes the biosynthesis and physio-chemical characterization of AgNPs. From Fourier transform infrared spectroscopy (FTIR) analysis, it was identified that the water soluble fractions of the sea grass mainly responsible for reduction of ionic silver (Ag+) into (Ag0) nano-ranged particles and also they act as stabilizing agent to sustain the durability of NPs for long period of time. Further, synthesized AgNPs shows potential cytotoxicity against human lung cancer A549 cells (LD50-100 μg/ml). The overall results suggest that C. serrulata is a valuable bioresource to generate rapid and eco-friendly bioactive AgNPs towards cancer therapy.

Retention of silver nano-particles and silver ions in calcareous soils: Influence of soil properties.

PubMed

Rahmatpour, Samaneh; Shirvani, Mehran; Mosaddeghi, Mohammad R; Bazarganipour, Mehdi

2017-05-15

The rapid production and application of silver nanoparticles (AgNPs) have led to significant release of AgNPs into the terrestrial environments. Once released into the soil, AgNPs could enter into different interactions with soil particles which play key roles in controlling the fate and transport of these nanoparticles. In spite of that, experimental studies on the retention of AgNPs in soils are very scarce. Hence, the key objective of this research was to find out the retention behavior of AgNPs and Ag(I) ions in a range of calcareous soils. A second objective was to determine the extent to which the physico-chemical properties of the soils influence the Ag retention parameters. To this end, isothermal batch experiments were used to determine the retention of Poly(vinylpyrrolidinone)-capped AgNPs (PVP-AgNPs) and Ag(I) ions by nine calcareous soils with a diversity of physico-chemical properties. The results revealed that the retention data for both PVP-AgNPs and Ag(I) ions were well described by the classical Freundlich and Langmuir isothermal equations. The retention of PVP-AgNPs and Ag(I) ions was positively correlated to clay and organic carbon (OC) contents as well as electrical conductivity (EC), pH, and cation exchange capacity (CEC) of the soils. Due to multicolinearity among the soil properties, principal component analysis (PCA) was used to group the soil properties which affect the retention of PVP-AgNPs and Ag(I) ions. Accordingly, we identified two groups of soil properties controlling retention of PVP-AgNPs and Ag(I) ions in the calcareous soils. The first group comprised soil solid phase parameters like clay, OC, and CEC, which generally control hetero-aggregation and adsorption reactions and the second group included soil solution variables such as EC and pH as well as Cl - and Ca 2+ concentrations, which are supposed to mainly affect homo-aggregation and precipitation reactions. Copyright © 2017. Published by Elsevier Ltd.

Synthesis and properties of nanocrystalline copper indium oxide thin films deposited by Rf magnetron sputtering.

PubMed

Singh, Mandeep; Singh, V N; Mehta, B R

2008-08-01

Nanocrystalline copper indium oxide (CuInO2) thin films with particle size ranging from 25 nm to 71 nm have been synthesized from a composite target using reactive Rf magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) combined with glancing angle X-ray diffraction (GAXRD) analysis confirmed the presence of delafossite CuInO2 phase in these films. The optical absorption studies show the presence of two direct band gaps at 3.3 and 4.3 eV, respectively. The resistance versus temperature measurements show thermally activated hopping with activation energy of 0.84 eV to be the conduction mechanism.

Polymer blend of PLA/PHBV based bionanocomposites reinforced with nanocrystalline cellulose for potential application as packaging material.

PubMed

Dasan, Y K; Bhat, A H; Ahmad, Faiz

2017-02-10

The current research discusses the development of poly (lactic acid) (PLA) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced nanocrystalline cellulose bionanocomposites. The nanocrystalline cellulose was derived from waste oil palm empty fruit bunch fiber by acid hydrolysis process. The resulting nanocrystalline cellulose suspension was then surface functionalized by TEMPO-mediated oxidation and solvent exchange process. Furthermore, the PLA/PHBV/nanocrystalline cellulose bionanocomposites were produced by solvent casting method. The effect of the addition of nanocrystalline cellulose on structural, morphology, mechanical and barrier properties of bionanocomposites was investigated. The results revealed that the developed bionanocomposites showed improved mechanical properties and decrease in oxygen permeability rate. Therefore, the developed bio-based composite incorporated with an optimal composition of nanocrystalline cellulose exhibits properties as compared to the polymer blend. Copyright © 2016 Elsevier Ltd. All rights reserved.

Size-dependent Hamaker constants for silver and gold nanoparticles

NASA Astrophysics Data System (ADS)

Pinchuk, Pavlo; Jiang, Ke

2015-08-01

Hamaker-Lifshitz constants are material specific constants that are used to calculate van der Waals interaction forces between small particles in solution. Typically, these constants are size-independent and material specific. According to the Lifshitz theory, the Hamaker-Lifshitz constants can be calculated by taking integrals that include the dielectric permittivity, as a function of frequency, of the interacting particles and the medium around particles. The dielectric permittivity of interacting metal nanoparticles can be calculated using the Drude model, which is based on the assumption of motion of free conducting electrons. For bulk metals, the Drude model does not predict any sizedependence of the dielectric permittivity. However, the conducting electrons in small noble metal nanoparticles (R ~ 10nm) exhibit surface scattering, which changes the complex permittivity function. In this work, we show theoretically that scattering of the free conducting electrons inside silver and gold nanoparticles with the size of 1 - 50 nm leads to size-dependent dielectric permittivity and Hamaker-Lifshitz constants. We calculate numerically the Hamaker-Lifshitz constants for silver and gold nanoparticles with different diameters. The results of the study might be of interests for understanding colloidal stability of metal nanoparticles.

Framework Stability of Nanocrystalline NaY in Aqueous Solution at Varying pH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petushkov, Anton; Freeman, Jasmine; Larsen, Sarah C.

Nanocrystalline zeolites (with crystal sizes of less than 50 nm) are versatile, porous nanomaterials with potential applications in a broad range of areas including bifunctional catalysis, drug delivery, environmental protection, and sensing, to name a few. The characterization of the properties of nanocrystalline zeolites on a fundamental level is critical to the realization of these innovative applications. Nanocrystalline zeolites have unique surface chemistry that is distinct from conventional microcrystalline zeolite materials and that will result in novel applications. In the proposed work, magnetic resonance techniques (solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR)) will be used tomore » elucidate the structure and reactivity of nanocrystalline zeolites and to motivate bifunctional applications. Density functional theory (DFT) calculations will enhance data interpretation through chemical shift, quadrupole coupling constant, g-value and hyperfine calculations.« less

Utilization of biogenic tea waste silver nanoparticles for the reduction of organic dyes

NASA Astrophysics Data System (ADS)

Kaur, H.; Jaryal, N.

2018-05-01

Eco-friendly synthesis of nanoparticles is the need of the society today. Present study has been undertaken to investigate the greener approach for the preparation of medicinally and chemically important nanoparticles. Tea waste has been taken to synthesis silver nanoparticles. The nanoparticles are characterized by x-ray Diffraction, and Transmission Emission Microscopy studies. The particle size varied from 2 to 34 nm. These silver nanoparticles were evaluated for their reducing activity against four organic dyes viz crystal violet, methylene blue, Congo red and brilliant green. The particles exhibited good catalytic activity against crystal violet, methylene blue and brilliant green but no activity was visible for Congo red. Furthermore, AgNPs shows very promising and prominent antioxidant activity.

Kyllinga brevifolia mediated greener silver nanoparticles

NASA Astrophysics Data System (ADS)

Isa, Norain; Bakhari, Nor Aziyah; Sarijo, Siti Halimah; Aziz, Azizan; Lockman, Zainovia

2017-12-01

Kyllinga brevifolia extract (KBE) was studied in this research as capping as well as reducing agent for the synthesis of greener plant mediated silver nanoparticles. This research was conducted in order to identify the compounds in the KBE that probable to work as reductant for the synthesis of Kyllinga brevifolia-mediated silver nanoparticles (AgNPs). Screening test such as Thin Layer Chromatography (TLC), Fourier Transform Infra-Red (FTIR), Carlo Erba Elemental analysis and Gas Chromatography-Mass Spectroscopy (GCMS) were used in identifying the natural compounds in KBE. The as-prepared AgNPs were characterized by UV-vis spectroscopy (UV-vis), Transmission Electron Microscope (TEM) and X-ray Diffraction (XRD). The TEM images showed that the as-synthesized silver have quasi-spherical particles are distributed uniformly with a narrow distribution from 5 nm to 40 nm. The XRD results demonstrated that the obtained AgNPs were face centre-cubic (FCC) structure. The catalytic activity of AgNPs on reduction of methylene blue (MB) using sodium borohydride (SB) was analyzed using UV-vis spectroscopy. This study showed that the efficacy of mediated AgNPs in catalysing the reduction of MB.

Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2014-11-01

1 ASETSDefense 2014 Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative Ruben A. Prado, CEF...COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative...coatings as a Hard Chrome (EHC) electroplating alternative for DoD manufacturing and repair. – Fully define deposition parameters and properties

Low-temperature synthesis of nanocrystalline ZrC coatings on flake graphite by molten salts

NASA Astrophysics Data System (ADS)

Ding, Jun; Guo, Ding; Deng, Chengji; Zhu, Hongxi; Yu, Chao

2017-06-01

A novel molten salt synthetic route has been developed to prepare nanocrystalline zirconium carbide (ZrC) coatings on flake graphite at 900 °C, using Zr powder and flake graphite as the source materials in a static argon atmosphere, along with molten salts as the media. The effects of different molten salt media, the sintered temperature, and the heat preservation time on the phase and microstructure of the synthetic materials were investigated. The ZrC coatings formed on the flake graphite were uniform and composed of nanosized particles (30-50 nm). With an increase in the reaction temperature, the ZrC nanosized particles were more denser, and the heat preservation time and thickness of the ZrC coating also increased accordingly. Electron microscopy was used to observe the ZrC coatings on the flake graphite, indicating that a "template mechanism" played an important role during the molten salt synthesis.

Model for temperature-dependent magnetization of nanocrystalline materials

NASA Astrophysics Data System (ADS)

Bian, Q.; Niewczas, M.

2015-01-01

A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

Solid state synthesis of starch-capped silver nanoparticles.

PubMed

Hebeish, A; Shaheen, Th I; El-Naggar, Mehrez E

2016-06-01

The present research addresses the establishment of a technique which is solely devoted to environmentally friendly one-pot green synthesis of dry highly stable powdered silver nanoparticles (AgNPs) using starch as both reductant and stabilizing agent in the presence of sodium hydroxide. It is believed that the sodium hydroxide can improve the reduction potential of starch. Thus when the alkali treated starch is submitted to addition of silver nitrate (AgNO3), the alkali treated starch induces the well-established dual role of starch; reduction of silver ions (Ag(+)) to AgNPs and capping the as-formed AgNPs to prevent them from further growth and agglomeration. Beside assessment of AgNPs formation, structural and morphological characteristics of AgNPs are investigated by making use of UV-vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, FT-IR and X-ray diffraction (XRD) analysis. Research outputs signify (a) the absorbance around 410-420nm in the UV-vis spectra of AgNPs appears most, probably owing to the presence of nanosized silver particles and the intensity of this peak increases by increasing AgNO3 concentration; (b) that highly stable AgNPs with well-dispersed particle are successfully prepared using the present research-based innovation; (c) that the size of AgNPs does not exceed 30nm with sphere-like morphology even at the highest Ag(+) concentration employed during synthesis operation; (d) that the XRD and FT-IR confirm the successful preparation of pure AgNPs without noticeable impurities; (d) and that the one-pot synthesis of powdered AgNPs in large scale is clean and easily operated and easily transportation which may be applied as per demands of industries such as textile and painting industry. Copyright © 2016. Published by Elsevier B.V.

Preparation of high-quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder.

PubMed

Riedl, Thomas; Gemming, Thomas; Mickel, Christine; Eymann, Konrad; Kirchner, Alexander; Kieback, Bernd

2012-06-01

This article explores the achievable transmission electron microscopy specimen thickness and quality by using three different preparation methods in the case of a high-strength nanocrystalline Cu-Nb powder alloy. Low specimen thickness is essential for spatially resolved analyses of the grains in nanocrystalline materials. We have found that single-sided as well as double-sided low-angle Ar ion milling of the Cu-Nb powders embedded into epoxy resin produced wedge-shaped particles of very low thickness (<10 nm) near the edge. By means of a modified focused ion beam lift-out technique generating holes in the lamella interior large micrometer-sized electron-transparent regions were obtained. However, this lamella displayed a higher thickness at the rim of ≥30 nm. Limiting factors for the observed thicknesses are discussed including ion damage depths, backscattering, and surface roughness, which depend on ion type, energy, current density, and specimen motion. Finally, sections cut by ultramicrotomy at low stroke rate and low set thickness offered vast, several tens of square micrometers uniformly thin regions of ∼10-nm minimum thickness. As major drawbacks, we have detected a thin coating on the sections consisting of epoxy deployed as the embedding material and considerable nanoscale thickness variations. Copyright © 2011 Wiley Periodicals, Inc.

Synthesis and characterization of silver nanoparticle composite with poly(p-Br-phenylsilane).

PubMed

Kim, Myoung-Hee; Lee, Jun; Mo, Soo-Yong; Woo, Hee-Gweon; Yang, Kap Seung; Kim, Bo-Hye; Lee, Byeong-Gweon; Sohn, Honglae

2012-05-01

The one-pot synthesis and characterization of silver nanoparticle-poly(p-Br-phenylsilane) composites have been carried out. The conversion of silver(+1) salt to stable silver(0) nanoparticles is promoted by poly(p-Br-phenylsilane), Br-PPS possessing both possible reactive Si-H bonds in the polymer backbone and C-Br bonds in the substituents. The composites were characterized using XRD, TEM, FE-SEM, and solid-state UV-vis analytical techniques. TEM and FE-SEM data show the formation of the composites where large number of silver nanoparticles (less than 30 nm of size) are well dispersed throughout the Br-PPS matrix. XRD patterns are consistent with that for fcc-typed silver. The elemental analysis for Br atom and the polymer solubility confirm that the cleavage of C-Br bond and the Si-Br dative bonding were not occurred appreciably at ambient temperature. Nonetheless, TGA data suggest that some sort of cross-linking was occurred at high temperature. The size and processability of such nanoparticles depend on the ratio of metal to Br-PPS. In the absence of Br-PPS, most of the silver particles undergo macroscopic aggregation, which indicates that the polysilane is necessary for stabilizing the silver nanoparticles.

Printed silver nanowire antennas with low signal loss at high-frequency radio.

PubMed

Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

2012-05-21

Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.

Effect of silver on the shape of palladium nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Dikshita, E-mail: dgmonugupta@gmail.com; Barman, P. B.; Hazra, S. K.

We report a facile route to prepare palladium-silver nanoparticles at considerably low temperature. First the controlled synthesis of palladium nanoparticles was performed via reduction of sodium tetrachloropalladate (II) in ethylene glycol in the presence of PVP(polyvinylpyrrolidone) as capping agent. The reaction was carried out at three different temperatures-80°C, 100°C and 120°C for one hour. Short reaction time and low synthesis temperature adds advantage to this method over others. Formed palladium nanoparticles were nearly spherical with the average particle size of 7.5±0.5 nm, 9.5±0.5 nm and 10.5±0.5 nm at 80°C, 100°C and 120°C respectively. Secondly, the palladium-silver nanoparticles were prepared bymore » the simultaneous reduction of palladium and silver from their respective precursors in ethylene glycol at 100°C (optimized temperature). The shape and size distribution was studied by TEM (Transmission Electron Microscopy). The role of silver in transforming the shape of palladium nanoparticles from spherical to triangular has been discussed. Spherical symmetry of palladium nanoparticles is disturbed by the interaction of silver ions on the crystal facets of palladium nanoparticles. From UV-vis spectra, the absorption maxima of palladium nanoparticles at 205 nm and absorption maxima of palladium-silver nanoparticles at 272 nm revealed the partial evidence of their formation.« less

Preferential Interaction of Na+ over K+ to Carboxylate-functionalized Silver Nanoparticles

EPA Science Inventory

Elucidating mechanistic interactions between specific ions (Na+/ K+) and nanoparticle surfaces to alter particle stability in polar media has received little attention. We investigated relative preferential binding of Na+ and K+ to carboxylate-functionalized silver nanoparticles ...

Synthesis of silver/silver chloride/graphene oxide composite and its surface-enhanced Raman scattering activity and self-cleaning property

NASA Astrophysics Data System (ADS)

Zhao, Nan; Fei, Xiao; Cheng, Xiaonong; Yang, Juan

2017-09-01

Recently, silver nanoparticles decorated with graphene and graphene oxide (GO) sheets can be employed as surface-enhanced Raman scattering (SERS) substrates. However, their SERS activity on macromolecular compound detection is all one-time process. In order to solve this issue and decrease the cost of routine SERS detection, silver/silver chloride (Ag/AgCl) with photocatalytic activity under visible light was introduced. In this study, a novel, simple and clean approach is carried out for synthesis of the Ag/AgCl/GO composite. The Ag/AgCl colloidal solution is obtained by hydrothermal method and then mixed with GO solution to obtain the Ag/AgCl/GO composite using a facile electrostatic self-assembly method. Results showed that the Ag/AgCl/GO composite has the optimized SERS activity to Rhodamine 6G molecules with the maximum enhancement factor value of 3.8×107. Furthermore, the Ag/AgCl particles with high efficient and stable photocatalytic activity under visible light lead to an outstanding self-cleaning property of the Ag/AgCl/GO composite.

Interactions between colloidal silver and photosynthetic pigments located in cyanobacteria fragments and in solution.

PubMed

Siejak, Przemysław; Frackowiak, Danuta

2007-09-25

Changes in the yield of the fluorescence emitted by pigments of photosynthetic organisms could be used for the establishment of the presence of some toxic substances. The presence of colloidal metals can be indicated by enhancement of pigments' emission as a result of plasmons generation. The spectra of the pigments of cyanobacterium Synechocystis located in the bacterium fragments and in solutions with and without colloidal silver additions have been measured. The quantum yield of the pigments' fluorescence in solution has been observed to increase at some wavelength of excitation, while the fluorescence of the pigments in the bacteria fragments has been only quenched as a consequence of interactions with colloidal silver particles. Close contact between pigment molecules located in bacteria fragments and silver particles is probably not possible. We plan in future to investigate the influence of other, more typical metal pollutants of water, using similar spectral methods and several other photosynthetic bacteria pigments, in solution, in cell fragments and in the whole bacteria organisms.

Synthesis, characterization and biocompatibility of ``green'' synthesized silver nanoparticles using tea polyphenols

NASA Astrophysics Data System (ADS)

Moulton, Michael C.; Braydich-Stolle, Laura K.; NadagoudaPresent Address: Pegasus Technical Services, 46 E. Hollister Street, Cincinnati, 45219, Ohio, Usa., Mallikarjuna N.; Kunzelman, Samantha; Hussain, Saber M.; Varma, Rajender S.

2010-05-01

Since ancient times, people have taken advantage of the antimicrobial effects of colloidal silver particles. Aside from the medical prospects, silver nanoparticles are found in a wide range of commercially available consumer products ranging from cosmetics to household cleansers. Current synthetic methods for creating silver nanoparticles typically call for potentially hazardous chemicals, extreme heat, and produce environmentally dangerous byproducts. Therefore, it is essential that novel ``green'' synthesis of nanoparticles becomes a reality, and it is imperative to fully analyze the potential toxic effects of these nanoparticles. In this study, we have shown that by reducing silver nitrate in solutions of tea extract or epicatechin of varying concentrations, spherical silver nanoparticles were formed that had controllable size distributions depending on the concentration of tea extract or epicatechin in the samples. Our ultra-resolution microscopy demonstrated that the nanoparticles were in fact interacting with the keratinocytes. Furthermore, evaluation of mitochondrial function (MTS) to assess cell viability and membrane integrity (LDH) in human keratinocytes showed that the silver nanoparticles were nontoxic. These results demonstrated that these nanoparicles are potentially biocompatible and warrant further evaluation in other biological systems.

Multifunctionality of nanocrystalline lanthanum ferrite

NASA Astrophysics Data System (ADS)

Rai, Atma; Thakur, Awalendra K.

2016-05-01

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

Multifunctionality of nanocrystalline lanthanum ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K.; Centre for Energy and Environment, Indian Institute of Technology Patna 800013 India

2016-05-06

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanummore » ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.« less

Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature.

PubMed

Sedlacik, Michal; Pavlinek, Vladimir; Peer, Petra; Filip, Petr

2014-05-14

Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C.

Three strategies to stabilise nearly monodispersed silver nanoparticles in aqueous solution

NASA Astrophysics Data System (ADS)

Stevenson, Amadeus PZ; Blanco Bea, Duani; Civit, Sergi; Antoranz Contera, Sonia; Iglesias Cerveto, Alberto; Trigueros, Sonia

2012-02-01

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.

Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.

PubMed

Parakhonskiy, B V; Svenskaya, Yu I; Yashchenok, A М; Fattah, H A; Inozemtseva, O A; Tessarolo, F; Antolini, R; Gorin, D A

2014-06-01

An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1μm. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of high pressure homogenization and stirred bead milling for the production of nano-crystalline suspensions.

PubMed

Nakach, Mostafa; Authelin, Jean-René; Perrin, Marc-Antoine; Lakkireddy, Harivardhan Reddy

2018-05-19

Currently, the two technologies primarily used for the manufacturing of nano-crystalline suspensions using top down process (i.e. wet milling) are high pressure homogenization (HPH) and stirred bead milling (SBM). These two technologies are based upon different mechanisms, i.e., cavitation forces for HPH and shear forces for stirred bead milling. In this article, the HPH and SBM technologies are compared in terms of the impact of the suspension composition the process parameters and the technological configuration on milling performances and physical quality of the suspensions produced. The data suggested that both HPH and SBM are suitable for producing nano-crystalline suspensions, although SBM appeared more efficient than HPH, since the limit of milling (d 50 ) for SBM was found to be lower than that obtained with HPH (100 nm vs 200 nm). For both these technologies, regardless of the process parameters used for milling and the scale of manufacturing, the relationship of d 90 versus d 50 could be described by a unique master curve (technology signature of milling pathway) outlining that the HPH leads to more uniform particle size distribution as compared to SBM. Copyright © 2018 Elsevier B.V. All rights reserved.

Structure and performance of anisotropic nanocrystalline Nd-Fe-B magnets fabricated by high-velocity compaction followed by deformation

NASA Astrophysics Data System (ADS)

Zhao, L. Z.; Deng, X. X.; Yu, H. Y.; Guan, H. J.; Li, X. Q.; Xiao, Z. Y.; Liu, Z. W.; Greneche, J. M.

2017-12-01

High-velocity compaction (HVC) has been proposed as an effective approach for the fabrication of nanocrystalline Nd-Fe-B magnets. In this work, the effect of powder size on the density of HVCed magnets has been studied and the anisotropic nanocrystalline Nd-Fe-B magnets were prepared by HVC followed by hot deformation (HD). It is found that a proper particle size range is beneficial to high density. The investigations on the microstructure, magnetic domain structure, and hyperfine structure, indicate that the deformed grain structure and the magnetic domain structure with uniform paramagnetic grain boundary phase give good magnetic properties of HVC + HDed magnets. These magnets also have good mechanical and anti-corrosion properties. The results indicate that HVC is not only a near-net-shape, room temperature and binder-free process but is also able to maintain uniform nanostructure and to achieve good magnetic properties in both isotropic and anisotropic magnets. As a result, HVC can be employed as an ideal alternative process for bonding or hot pressing for the conventional MQI, MQII and MQIII magnets.

Arsenic sorption by nanocrystalline magnetite: an example of environmentally promising interface with geosphere.

PubMed

Bujňáková, Z; Baláž, P; Zorkovská, A; Sayagués, M J; Kováč, J; Timko, M

2013-11-15

In this paper, the sorption of arsenic onto nanocrystalline magnetite mineral Fe3O4 was studied in a model system. Nanocrystalline magnetite was produced by mechanical activation in a planetary ball mill from natural microcrystalline magnetite. As a consequence of milling, the specific surface area increased from 0.1m(2)/g to 11.9 m(2)/g and the surface site concentration enhanced from 2.2 sites/nm(2) to 8.4 sites/nm(2). These changes in surface properties of magnetite lead to the enhancement of arsenic removal from model system. The best sorption ability was achieved with magnetite sample activated for 90 min. In this case the sample was able to absorb around 4 mg/g. The structural changes of magnetite were also observed and the new hematite phase was detected after 120 min of milling. A good correlation between the decreasing particle size, increasing specific surface area and reduction of saturation magnetization was found. In desorption study, KOH and NaOH were found as the best eluents where more than 70% of arsenic was released back into the solution. The principal novelty of the paper is that mineral magnetite, truly one nature's gift can be used after "smart" milling (mechanical activation) as an effective arsenic sorbent. Copyright © 2013 Elsevier B.V. All rights reserved.

Nanocarbon Allotropes-Graphene and Nanocrystalline Diamond-Promote Cell Proliferation.

PubMed

Verdanova, Martina; Rezek, Bohuslav; Broz, Antonin; Ukraintsev, Egor; Babchenko, Oleg; Artemenko, Anna; Izak, Tibor; Kromka, Alexander; Kalbac, Martin; Hubalek Kalbacova, Marie

2016-05-01

Two profoundly different carbon allotropes - nanocrystalline diamond and graphene - are of considerable interest from the viewpoint of a wide range of biomedical applications including implant coating, drug and gene delivery, cancer therapy, and biosensing. Osteoblast adhesion and proliferation on nanocrystalline diamond and graphene are compared under various conditions such as differences in wettability, topography, and the presence or absence of protein interlayers between cells and the substrate. The materials are characterized in detail by means of scanning electron microscopy, atomic force microscopy, photoelectron spectroscopy, Raman spectroscopy, and contact angle measurements. In vitro experiments have revealed a significantly higher degree of cell proliferation on graphene than on nanocrystalline diamond and a tissue culture polystyrene control material. Proliferation is promoted, in particular, by hydrophobic graphene with a large number of nanoscale wrinkles independent of the presence of a protein interlayer, i.e., substrate fouling is not a problematic issue in this respect. Nanowrinkled hydrophobic graphene, thus, exhibits superior characteristics for those biomedical applications where high cell proliferation is required under differing conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of voids distribution on the deformation behavior of nanocrystalline palladium

NASA Astrophysics Data System (ADS)

Bachurin, D. V.

2018-07-01

Uniaxial deformation of three-dimensional nanocrystalline palladium containing porosity in the form of voids was investigated by means of molecular dynamics method. Simulations were performed at temperature of 300 K and at a constant strain rate of 108s-1. Two cases of voids distribution were considered: random and at triple or quadrupole junctions. It has been revealed that both the voids distribution and subsequent annealing at elevated temperature influence the deformation behavior of nanocrystalline palladium. In particular, the presence of voids at grain junctions results in a reduction of the Young's modulus and more pronounced softening effect during plastic deformation. The subsequent annealing evokes shrinkage of voids and strengthening effect. Contribution of grain boundary accommodation processes into both elastic and plastic deformation of nanocrystalline materials is discussed.

Electrode characteristics of nanocrystalline (Zr, Ti)(V, Cr, Ni) 2.41 compound

NASA Astrophysics Data System (ADS)

Majchrzycki, W.; Jurczyk, M.

The electrochemical properties of nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 alloy, which has the hexagonal C14 type structure, have been investigated. This material has been prepared using mechanical alloying (MA) followed by annealing. The amorphous phase forms directly from the starting mixture of the elements, without other phase formation. Heating the MA samples at 1070 K for 0.5 h resulted in the creation of ordered alloy. This alloy was used as negative electrode for Ni-MH x battery. The electrochemical results show very little difference between the nanocrystalline and polycrystalline powders, as compared with the substantial difference between these and the amorphous powder. In the annealed nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 powders discharging capacities up to 150 mA h g -1 (at 160 mA g -1 discharging current) have been measured. The properties of nanocrystalline electrode were attributed to the structural characteristics of the compound caused by mechanical alloying.

Synthesis and characterization of silver-copper core-shell nanoparticles using polyol method for antimicrobial agent

NASA Astrophysics Data System (ADS)

Hikmah, N.; Idrus, N. F.; Jai, J.; Hadi, A.

2016-06-01

Silver and copper nanoparticles are well-known as the good antimicrobial agent. The nano-size of particles influences in enhancing the antimicrobial activity. This paper discusses the effect of molarity on the microstructure and morphology of silver-copper core-shell nanoparticles prepared by a polyol method. In this study, silver-copper nanoparticles are synthesized through the green approach of polyol method using ethylene glycol (EG) as green solvent and reductant, and polyoxyethylene-(80)-sorbitan monooleate (Tween 80) as a nontoxic stabilizer. The phase and morphology of silver-copper nanoparticles are characterized by X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM) and Transmission electron microscope (TEM). The results XRD confirm the pure crystalline of silver and copper nanoparticles with face-centered cubic (FCC) structure. FESEM and TEM analysis confirm the existence of Ag and Cu nanoparticles in core-shell shape.

Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques

DOE PAGES

Durham, Jessica L.; Brady, Alexander B.; Cama, Christina A.; ...

2017-08-02

Here, the structure of pristine AgFeO 2 and phase makeup of Ag 0.2FeO1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2O 3 phases) was investigated using synchrotron x-ray diffraction. A new stacking-fault model was proposed for AgFeO2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2FeO 1.6 were investigated using ex-situ, in-situ, and operando characterization techniques. An amorphous γ-Fe 2O 3 component in the Ag 0.2FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2FeO 1.6 composites demonstrated differences in the structuralmore » evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex-situ x-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in-situ high energy x-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+yFe IIIFe IIyO 2 phase. The Li 1+yFe IIIFe IIyO 2 phase can then reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2FeO 1.6 composite, a substantial amorphous γ-Fe 2O 3 component is observed which discharges to rock salt LiFe 2O 3 and Fe 0 metal phase in the 3.5 – 1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.« less

Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durham, Jessica L.; Brady, Alexander B.; Cama, Christina A.

Here, the structure of pristine AgFeO 2 and phase makeup of Ag 0.2FeO1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2O 3 phases) was investigated using synchrotron x-ray diffraction. A new stacking-fault model was proposed for AgFeO2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2FeO 1.6 were investigated using ex-situ, in-situ, and operando characterization techniques. An amorphous γ-Fe 2O 3 component in the Ag 0.2FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2FeO 1.6 composites demonstrated differences in the structuralmore » evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex-situ x-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in-situ high energy x-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+yFe IIIFe IIyO 2 phase. The Li 1+yFe IIIFe IIyO 2 phase can then reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2FeO 1.6 composite, a substantial amorphous γ-Fe 2O 3 component is observed which discharges to rock salt LiFe 2O 3 and Fe 0 metal phase in the 3.5 – 1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.« less

Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques.

PubMed

Durham, Jessica L; Brady, Alexander B; Cama, Christina A; Bock, David C; Pelliccione, Christopher J; Zhang, Qing; Ge, Mingyuan; Li, Yue Ru; Zhang, Yiman; Yan, Hanfei; Huang, Xiaojing; Chu, Yong; Takeuchi, Esther S; Takeuchi, Kenneth J; Marschilok, Amy C

2017-08-23

The structure of pristine AgFeO 2 and phase makeup of Ag 0.2 FeO 1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2 O 3 phases) was investigated using synchrotron X-ray diffraction. A new stacking-fault model was proposed for AgFeO 2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2 FeO 1.6 were investigated using ex situ, in situ, and operando characterization techniques. An amorphous γ-Fe 2 O 3 component in the Ag 0.2 FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2 FeO 1.6 composites demonstrated differences in the structural evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex situ X-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in situ high energy X-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag 0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+y Fe III Fe II y O 2 phase. The Li 1+y Fe III Fe II y O 2 phase can then reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2 FeO 1.6 composite, a substantial amorphous γ-Fe 2 O 3 component is observed which discharges to rock salt LiFe 2 O 3 and Fe 0 metal phase in the 3.5-1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.

Antioxidant properties of biohybrids based on liposomes and sage silver nanoparticles.

PubMed

Barbinta-Patrascu, Marcela Elisabeta; Bunghez, Ioana-Raluca; Iordache, Stefan Marian; Badea, Nicoleta; Fierascu, Radu-Claudiu; Ion, Rodica Mariana

2013-03-01

This paper is aimed to describe a simple and rapid eco-friendly bottom-up approach for the preparation of antioxidant silver bionanostructures using a leaf extract from sage (Salvia officinalis L.). The bioreduction property of sage in the synthesis of silver nanoparticles was investigated by UV-VIS and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy. During their preparation, the particle size analysis was performed by using Dynamic Light Scattering technique. Ultrasonic irradiation was used to obtain sage silver nanoparticles. The morphology (size and shape) of the herbal silver nanoparticles was evaluated by Scanning Electron Microscopy that revealed the formation of spherical phytonanoparticles with size less than 80 nm. In order to increase their stability and their biocompatibility, the sage silver nanoparticles were introduced in two types of liposomes: soybean lecithin- and Chla-DPPC-lipid vesicles which were prepared by thin film hydration method. X-Ray Fluorescence analysis confirmed the silver presence in liposomes/sage-AgNPs biohybrids. The stability of liposomes/herbal AgNPs bioconstructs was checked by zeta potential measurements. The most stable biohybrids: Chla-DPPC/sage-AgNPs with zeta potential value of -34.2 mV, were characterized by Atomic Force Microscopy revealing the spherical and quasi-spherical shaped profiles of these nanobiohybrids with size less than 96 nm. The antioxidant activity of the silver bionanostructures was evaluated using chemiluminescence assay. The developed eco-friendly silver phytonanostructures based on lipid membranes, nanosilver and sage extract, manifest strong antioxidant properties (between 86.5% and 98.6%).

Nanocrystalline High-Entropy Alloys: A New Paradigm in High-Temperature Strength and Stability.

PubMed

Zou, Yu; Wheeler, Jeffrey M; Ma, Huan; Okle, Philipp; Spolenak, Ralph

2017-03-08

Metals with nanometer-scale grains or nanocrystalline metals exhibit high strengths at ambient conditions, yet their strengths substantially decrease with increasing temperature, rendering them unsuitable for usage at high temperatures. Here, we show that a nanocrystalline high-entropy alloy (HEA) retains an extraordinarily high yield strength over 5 GPa up to 600 °C, 1 order of magnitude higher than that of its coarse-grained form and 5 times higher than that of its single-crystalline equivalent. As a result, such nanostructured HEAs reveal strengthening figures of merit-normalized strength by the shear modulus above 1/50 and strength-to-density ratios above 0.4 MJ/kg, which are substantially higher than any previously reported values for nanocrystalline metals in the same homologous temperature range, as well as low strain-rate sensitivity of ∼0.005. Nanocrystalline HEAs with these properties represent a new class of nanomaterials for high-stress and high-temperature applications in aerospace, civilian infrastructure, and energy sectors.

Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

NASA Astrophysics Data System (ADS)

Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

2014-09-01

The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties.

PubMed

Pazos, Elena; Sleep, Eduard; Rubert Pérez, Charles M; Lee, Sungsoo S; Tantakitti, Faifan; Stupp, Samuel I

2016-05-04

Silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal-organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryotic cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.

Orientation of N-(1-(2-chlorophenyl)-2-(2-nitrophenyl)ethyl)-4-methylbenzenesulfonamide on silver nanoparticles: SERS studies.

PubMed

Anuratha, M; Jawahar, A; Umadevi, M; Sathe, V G; Vanelle, P; Terme, T; Meenakumari, V; Milton Franklin Benial, A

2014-10-15

In the present study, the silver nanoparticles were synthesized using a solution combustion method with urea as fuel. The prepared silver nanoparticles show an FCC crystalline structure with particle size of 59nm. FESEM image shows the prepared silver is a rod like structure. The surface-enhanced Raman scattering (SERS) spectrum indicates that the N-(1-(2-chlorophenyl)-2-(2-nitrophenyl)ethyl)-4-methylbenzenesulfonamide (CS) molecule adsorbed on the silver nanoparticles. The spectral analysis reveals that the sulfonamide is adsorbed by tilted orientation on the silver surface. The Hatree Fock calculations were also performed to predict the vibrational motions of CS. This present investigation has been a model system to deduce the interaction of drugs with DNA. Copyright © 2014 Elsevier B.V. All rights reserved.

Intravenous Exposure of Pregnant Mice to Silver Nanoparticles: Silver Tissue Distribution and Effects in Maternal and Extra-Embryonic Tissues and Embryos

NASA Astrophysics Data System (ADS)

Austin, Carlye Anne

concentration in visceral yolk sac and low silver concentration in embryos, suggests that visceral yolk sac tissue mitigates AgNP transfer to embryos. No significant treatment-related effects on embryo morphology or tissue histology were detected. Chapter three constitutes an expanded study of silver distribution in pregnant mice and developing embryos, with the addition of 10 nm AgNP treatment groups and examination of fetuses at GD16. Very low concentrations of silver were measured in GD10 embryos and GD16 fetuses following 10 nm AgNP treatment or in GD16 fetuses following 50 nm AgNP treatment. Highest silver concentrations were measured in maternal liver, spleen, and visceral yolk sac. AgNP particle size (10 or 50 nm) did not consistently affect silver tissue distribution. At GD10, 50 nm AgNP treatment resulted in significantly higher silver concentrations than 10 nm AgNP treatment for liver, spleen, and visceral yolk sac only; at GD16, in visceral yolk sac only, 10 nm AgNP treatment resulted in a significantly higher silver concentration than 50 nm AgNP treatment. In liver, spleen, visceral yolk sac, and uterus, absolute silver concentrations following 10 nm AgNP treatment were significantly lower at GD16 compared to GD10; the patterns of silver tissue distribution were similar at both time points. Silver nitrate and 10 nm AgNP treatments resulted in similar tissue concentrations in GD10 tissues with the exception of visceral yolk sac, for which the silver concentration was significantly higher after silver nitrate treatment. Silver distribution patterns were generally similar between 10 nm AgNP and silver nitrate treatments. No histological abnormalities were noted in maternal tissues, extra-embryonic tissues, or embryos. A significantly increased incidence of developmentally young (for gestational age) GD10 embryos was seen following 10 nm AgNP treatment; no significant morphological effects were observed in embryos or maternal tissues. Further research will be needed to

Occupational exposure limit for silver nanoparticles: considerations on the derivation of a general health-based value.

PubMed

Weldon, Brittany A; M Faustman, Elaine; Oberdörster, Günter; Workman, Tomomi; Griffith, William C; Kneuer, Carsten; Yu, Il Je

2016-09-01

With the increased production and widespread commercial use of silver nanoparticles (AgNPs), human and environmental exposures to silver nanoparticles are inevitably increasing. In particular, persons manufacturing and handling silver nanoparticles and silver nanoparticle containing products are at risk of exposure, potentially resulting in health hazards. While silver dusts, consisting of micro-sized particles and soluble compounds have established occupational exposure limits (OELs), silver nanoparticles exhibit different physicochemical properties from bulk materials. Therefore, we assessed silver nanoparticle exposure and related health hazards in order to determine whether an additional OEL may be needed. Dosimetric evaluations in our study identified the liver as the most sensitive target organ following inhalation exposure, and as such serves as the critical target organ for setting an occupational exposure standard for airborne silver nanoparticles. This study proposes an OEL of 0.19 μg/m(3) for silver nanoparticles derived from benchmark concentrations (BMCs) from subchronic rat inhalation toxicity assessments and the human equivalent concentration (HEC) with kinetic considerations and additional uncertainty factors. It is anticipated that this level will protect workers from potential health hazards, including lung, liver, and skin damage.

Green synthesis, antimicrobial and cytotoxic effects of silver nanoparticles using Eucalyptus chapmaniana leaves extract.

PubMed

Sulaiman, Ghassan Mohammad; Mohammed, Wasnaa Hatif; Marzoog, Thorria Radam; Al-Amiery, Ahmed Abdul Amir; Kadhum, Abdul Amir H; Mohamad, Abu Bakar

2013-01-01

To synthesize silver nanopaticles from leaves extract of Eucalyptus chapmaniana (E. chapmaniana) and test the antimicrobial of the nanoparticles against different pathogenic bacteria, yeast and its toxicity against human acute promyelocytic leukemia (HL-60) cell line. Ten milliliter of leaves extract was mixed with 90 mL of 0.01 mmol/mL or 0.02 mmol/mL aqueous AgNO3 and exposed to sun light for 1 h. A change from yellowish to reddish brown color was observed. Characterization using UV-vis spectrophotometery and X-ray diffraction analysis were performed. Antimicrobial activity against six microorganisms was tested using well diffusion method and cytoxicity test using 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, a yellow tetrazole was obtained on the human leukemia cell line (HL-60). UV-vis spectral analysis showed silver surface plasmon resonance band at 413 nm. X-ray diffraction showed that the particles were crystalline in nature with face centered cubic structure of the bulk silver with broad beaks at 38.50° and 44.76°. The synthesized silver nanoparticles efficiently inhibited various pathogenic organisms and reduced viability of the HL-60 cells in a dose-dependent manner. It has been demonstrated that the extract of E. chapmaniana leaves are capable of producing silver nanoparticles extracellularly and the Ag nanoparticles are quite stable in solution. Further studies are needed to fully characterize the toxicity and the mechanisms involved with the antimicrobial and anticancer activity of these particles.

Production of nanocrystalline metal powders via combustion reaction synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frye, John G.; Weil, Kenneth Scott; Lavender, Curt A.

Nanocrystalline metal powders comprising tungsten, molybdenum, rhenium and/or niobium can be synthesized using a combustion reaction. Methods for synthesizing the nanocrystalline metal powders are characterized by forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and a base-soluble, ammonium precursor of tungsten, molybdenum, rhenium, or niobium in amounts that yield a stoichiometric burn when combusted. The combustion synthesis solution is then heated to a temperature sufficient to substantially remove water and to initiate a self-sustaining combustion reaction. The resulting powder can be subsequently reduced to metal form by heating in a reducing gas environment.

Grain growth in nanocrystalline iron and Fe-Al alloys

NASA Astrophysics Data System (ADS)

Mirzadeh, Hamed; Zomorodian, Amir

2010-02-01

The effects of the annealing temperature and time, cryomilling in liquid nitrogen, and the addition of aluminum powder on the thermal stability and grain growth behavior of nanocrystalline iron were modeled using the Artificial Neural Network (ANN) technique. The developed model can be used as a guide for the quantification of the grain growth by considering the effects of annealing temperature and time. The model also quantified the effect of Al on the thermal stability of cryomilled nanocrystalline Fe. The model results showed that the cryomilling of Fe has a tangible effect on the stabilization of the nanostructure.

Exposure-related health effects of silver and silver compounds: a review.

PubMed

Drake, Pamela L; Hazelwood, Kyle J

2005-10-01

A critical review of studies examining exposures to the various forms of silver was conducted to determine if some silver species are more toxic than others. The impetus behind conducting this review is that several occupational exposure limits and guidelines exist for silver, but the values for each depend on the form of silver as well as the individual agency making the recommendations. For instance, the American Conference of Governmental Industrial Hygienists has established separate threshold limit values for metallic silver (0.1 mg/m3) and soluble compounds of silver (0.01 mg/m3). On the other hand, the permissible exposure limit (PEL) recommended by the Occupational Safety and Health Administration and the Mine Safety and Health Administration and the recommended exposure limit set by the National Institute for Occupational Safety and Health is 0.01 mg/m3 for all forms of silver. The adverse effects of chronic exposure to silver are a permanent bluish-gray discoloration of the skin (argyria) or eyes (argyrosis). Most studies discuss cases of argyria and argyrosis that have resulted primarily from exposure to the soluble forms of silver. Besides argyria and argyrosis, exposure to soluble silver compounds may produce other toxic effects, including liver and kidney damage, irritation of the eyes, skin, respiratory, and intestinal tract, and changes in blood cells. Metallic silver appears to pose minimal risk to health. The current occupational exposure limits do not reflect the apparent difference in toxicities between soluble and metallic silver; thus, many researchers have recommended that separate PELs be established.

Evaluation of antimicrobial activity of silver nanoparticles for carboxymethylcellulose film applications in food packaging.

PubMed

Siqueira, Maria C; Coelho, Gustavo F; de Moura, Márcia R; Bresolin, Joana D; Hubinger, Silviane Z; Marconcini, José M; Mattoso, Luiz H C

2014-07-01

In this study, silver nanoparticles were prepared and incorporated into carboxymethylcellulose films to evaluate the antimicrobial activity for food packaging applications. The techniques carried out for material characterization were: infrared spectroscopy and thermal analysis for the silver nanoparticles and films, as well as particle size distribution for the nanoparticles and water vapor permeability for the films. The antimicrobial activity of silver nanoparticles prepared by casting method was investigated. The minimum inhibitory concentration (MIC) value of the silver nanoparticles to test Gram-positive (Enterococcus faecalis) and Gram-negative (Escherichia coli) microorganisms was carried out by the serial dilution technique, tested in triplicate to confirm the concentration used. The results were developed using the Mcfarland scale which indicates that the presence or absence of turbidity tube demonstrates the inhibition of bacteria in relation to the substance inoculated. It was found that the silver nanoparticles inhibited the growth of the tested microorganisms. The carboxymethylcellulose film embedded with silver nanoparticles showed the best antimicrobial effect against Gram-positive (E. faecalis) and Gram-negative (E. coli) bacteria (0.1 microg cm(-3)).

Phytosynthesis and Characterization of Silver Nanoparticles Using Callus of JATROPHA CURCAS: a Biotechnological Approach

NASA Astrophysics Data System (ADS)

Demissie, A. G.; Lele, S. S.

2013-06-01

The present study reports a rapid plant-based biosynthesis of silver nanoparticles using callus extract of Jatropha curcas L. The particle size and morphological analyses were carried out using Zetasizer, SEM, TEM. The physicochemical properties were monitored using UV-Vis spectroscopic, IR and DSC. The formation of silver nanoparticle was confirmed by using UV-Vis spectrophotometer and absorbance peaks at 421 nm. The silver nanoparticle was found to be a negatively charged with size ranging from 2 nm to 50 nm. The morphology of the nanoparticle is uniformly spherical and has a dispersion ratio of 0.14. The physicochemical study using DSC indicated significant thermal stability and crystalline nature of the nanoparticle. This intracellular biosynthesis of silver nanoparticles is simple, cheap and eco-friendly than other mechanical and chemical approaches.

Engineered Escherichia coli Silver-Binding Periplasmic Protein That Promotes Silver Tolerance

PubMed Central

Hall Sedlak, Ruth; Hnilova, Marketa; Grosh, Carolynn; Fong, Hanson; Baneyx, Francois; Schwartz, Dan; Sarikaya, Mehmet; Tamerler, Candan

2012-01-01

Silver toxicity is a problem that microorganisms face in medical and environmental settings. Through exposure to silver compounds, some bacteria have adapted to growth in high concentrations of silver ions. Such adapted microbes may be dangerous as pathogens but, alternatively, could be potentially useful in nanomaterial-manufacturing applications. While naturally adapted isolates typically utilize efflux pumps to achieve metal resistance, we have engineered a silver-tolerant Escherichia coli strain by the use of a simple silver-binding peptide motif. A silver-binding peptide, AgBP2, was identified from a combinatorial display library and fused to the C terminus of the E. coli maltose-binding protein (MBP) to yield a silver-binding protein exhibiting nanomolar affinity for the metal. Growth experiments performed in the presence of silver nitrate showed that cells secreting MBP-AgBP2 into the periplasm exhibited silver tolerance in a batch culture, while those expressing a cytoplasmic version of the fusion protein or MBP alone did not. Transmission electron microscopy analysis of silver-tolerant cells revealed the presence of electron-dense silver nanoparticles. This is the first report of a specifically engineered metal-binding peptide exhibiting a strong in vivo phenotype, pointing toward a novel ability to manipulate bacterial interactions with heavy metals by the use of short and simple peptide motifs. Engineered metal-ion-tolerant microorganisms such as this E. coli strain could potentially be used in applications ranging from remediation to interrogation of biomolecule-metal interactions in vivo. PMID:22286990

Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Khaydarov, R. R.; Khaydarov, R. A.; Estrin, Y.; Evgrafova, S.; Scheper, T.; Endres, C.; Cho, S. Y.

The bactericidal effect of silver nanoparticles obtained by a novel electrochemical method on Escherichia coli, Staphylococcus aureus, Aspergillus niger and Penicillium phoeniceum cultures has been studied. The tests conducted have demonstrated that synthesized silver nanoparticles — when added to water paints or cotton fabrics — show a pronounced antibacterial/antifungal effect. It was shown that smaller silver nanoparticles have a greater antibacterial/antifungal efficacy. The paper also provides a review of scientific literature with regard to recent developments in the field of toxicity of silver nanoparticles and its effect on environment and human health.

DLVO Approximation Methods for Predicting the Attachment of Silver Nanoparticles to Ceramic Membranes.

PubMed

Mikelonis, Anne M; Youn, Sungmin; Lawler, Desmond F

2016-02-23

This article examines the influence of three common stabilizing agents (citrate, poly(vinylpyrrolidone) (PVP), and branched poly(ethylenimine) (BPEI)) on the attachment affinity of silver nanoparticles to ceramic water filters. Citrate-stabilized silver nanoparticles were found to have the highest attachment affinity (under conditions in which the surface potential was of opposite sign to the filter). This work demonstrates that the interaction between the electrical double layers plays a critical role in the attachment of nanoparticles to flat surfaces and, in particular, that predictions of double-layer interactions are sensitive to boundary condition assumptions (constant charge vs constant potential). The experimental deposition results can be explained when using different boundary condition assumptions for different stabilizing molecules but not when the same assumption was assumed for all three types of particles. The integration of steric interactions can also explain the experimental deposition results. Particle size was demonstrated to have an effect on the predicted deposition for BPEI-stabilized particles but not for PVP.

Electrostatic separation for recycling silver, silicon and polyethylene terephthalate from waste photovoltaic cells

NASA Astrophysics Data System (ADS)

Zhang, Zisheng; Sun, Bo; Yang, Jie; Wei, Yusheng; He, Shoujie

2017-04-01

Electrostatic separation technology has been proven to be an effective and environmentally friendly way of recycling electronic waste. In this study, this technology was applied to recycle waste solar panels. Mixed particles of silver and polyethylene terephthalate, silicon and polyethylene terephthalate, and silver and silicon were separated with a single-roll-type electrostatic separator. The influence of high voltage level, roll speed, radial position corona electrode and angular position of the corona electrode on the separation efficiency was studied. The experimental data showed that separation of silver/polyethylene terephthalate and silicon/polyethylene terephthalate needed a higher voltage level, while separation of silver and silicon needed a smaller angular position for the corona electrode and a higher roll speed. The change of the high voltage level, roll speed, radial position of the corona electrode, and angular position of the corona electrode has more influence on silicon separation efficiency than silver separation efficiency. An integrated process is proposed using a two-roll-type corona separator for multistage separation of a mixture of these three materials. The separation efficiency for silver and silicon were found to reach 96% and 98%, respectively.

Uncapped silver nanoparticles synthesized by DC arc thermal plasma technique for conductor paste formulation

NASA Astrophysics Data System (ADS)

Shinde, Manish; Pawar, Amol; Karmakar, Soumen; Seth, Tanay; Raut, Varsha; Rane, Sunit; Bhoraskar, Sudha; Amalnerkar, Dinesh

2009-11-01

Uncapped silver nanoparticles were synthesized by DC arc thermal plasma technique. The synthesized nanoparticles were structurally cubic and showed wide particle size variation (between 20-150 nm). Thick film paste formulated from such uncapped silver nanoparticles was screen-printed on alumina substrates and the resultant `green' films were fired at different firing temperatures. The films fired at 600 °C revealed better microstructure properties and also yielded the lowest value of sheet resistance in comparison to those corresponding to conventional peak firing temperature of 850 °C. Our findings directly support the role of silver nanoparticles in substantially depressing the operative peak firing temperature involved in traditional conductor thick films technology.

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

NASA Astrophysics Data System (ADS)

Siegel, Jakub; Lyutakov, Oleksiy; Polívková, Markéta; Staszek, Marek; Hubáček, Tomáš; Švorčík, Václav

2017-10-01

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV-vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

Temperature evolution in silver nanoparticle doped PETN composite

NASA Astrophysics Data System (ADS)

Kameswari, D. P. S. L.; Kiran, P. Prem

2018-04-01

Optical absorption and the associated spatio-temporal evolution of temperature silver nanoparticles doped energetic material composite is presented. Silver nanoparticles of radii 10 - 150 nm are doped in Penta Erythrtol Tetra Nitrate (PETN), a secondary energetic material to form the composite materials. Of all the composites the ones doped with 35 nm sized nanoparticles have shown maximum absorption at excitation wavelength of 532 nm. The spatio-temporal evolution of temperature within these composites up on excitation with ns laser pulses of energy density 0.5 J/cm2 is studied. The role of particle sizes on the temperature of composites is studied and a maximum temperature of 2200 K at the nanoparticle interface is observed for 35 nm doped PETN composite.

Physicochemical study of natural fractionated biocolloid by asymmetric flow field-flow fractionation in tandem with various complementary techniques using biologically synthesized silver nanocomposites.

PubMed

Railean-Plugaru, Viorica; Pomastowski, Pawel; Kowalkowski, Tomasz; Sprynskyy, Myroslav; Buszewski, Boguslaw

2018-04-01

Asymmetric flow field-flow fractionation coupled with use of ultraviolet-visible, multiangle light scattering (MALLS), and dynamic light scattering (DLS) detectors was used for separation and characterization of biologically synthesized silver composites in two liquid compositions. Moreover, to supplement the DLS/MALLS information, various complementary techniques such as transmission electron spectroscopy, Fourier transform infrared spectroscopy, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used. The hydrodynamic diameter and the radius of gyration of silver composites were slightly larger than the sizes obtained by transmission electron microscopy (TEM). Moreover, the TEM results revealed the presence of silver clusters and even several morphologies, including multitwinned. Additionally, MALDI-TOF MS examination showed that the particles have an uncommon cluster structure. It can be described as being composed of two or more silver clusters. The organic surface of the nanoparticles can modify their dispersion. We demonstrated that the variation of the silver surface coating directly influenced the migration rate of biologically synthesized silver composites. Moreover, this study proves that the fractionation mechanism of silver biocolloids relies not only on the particle size but also on the type and mass of the surface coatings. Because silver nanoparticles typically have size-dependent cytotoxicity, this behavior is particularly relevant for biomedical applications. Graphical abstract Workflow for asymmetric flow field-flow fractionation of natural biologically synthesized silver nanocomposites.

Cytotoxic and genotoxic effects of silver nanoparticles in testicular cells.

PubMed

Asare, Nana; Instanes, Christine; Sandberg, Wiggo J; Refsnes, Magne; Schwarze, Per; Kruszewski, Marcin; Brunborg, Gunnar

2012-01-27

Serious concerns have been expressed about potential risks of engineered nanoparticles. Regulatory health risk assessment of such particles has become mandatory for the safe use of nanomaterials in consumer products and medicines; including the potential effects on reproduction and fertility, are relevant for this risk evaluation. In this study, we examined effects of silver particles of nano- (20nm) and submicron- (200nm) size, and titanium dioxide nanoparticles (TiO(2)-NPs; 21nm), with emphasis on reproductive cellular- and genotoxicity. Ntera2 (NT2, human testicular embryonic carcinoma cell line), and primary testicular cells from C57BL6 mice of wild type (WT) and 8-oxoguanine DNA glycosylase knock-out (KO, mOgg1(-/-)) genotype were exposed to the particles. The latter mimics the repair status of human testicular cells vs oxidative damage and is thus a suitable model for human male reproductive toxicity studies. The results suggest that silver nano- and submicron-particles (AgNPs) are more cytotoxic and cytostatic compared to TiO(2)-NPs, causing apoptosis, necrosis and decreased proliferation in a concentration- and time-dependent manner. The 200nm AgNPs in particular appeared to cause a concentration-dependent increase in DNA-strand breaks in NT2 cells, whereas the latter response did not seem to occur with respect to oxidative purine base damage analysed with any of the particles tested. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.