SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Silver

171

Silver nanoparticles supported on nanoscale silicate platelets (AgNP/NSP) possess interesting properties, including a large surface area and high biocide effectiveness. The nanohybrid of AgNP/NSP at a weight ratio 7/93 contains 5-nm Ag particles supported on the surface of platelets with dimensions of approximately 80×80×1 nm(3). The nanohybrid expresses a trend of lower cytotoxicity at the concentration of 8.75 ppm Ag and low genotoxicity. Compared with conventional silver ions and the organically dispersed AgNPs, the nanohybrid promotes wound healing. We investigated overall wound healing by using acute burn and excision wound healing models. Tests on both infected wound models of mice were compared among the AgNP/NSP, polymer-dispersed AgNPs, the commercially available Aquacel, and silver sulfadiazine. The AgNP/NSP nanohybrid was superior for wound appearance, but had similar wound healing rates, vascular endothelial growth factor (VEGF)-A levels and transforming growth factor (TGF)-β1 expressions to Aquacel and silver sulfadiazine.

Concepts: Wound healing, Angiogenesis, Coagulation, Platelet, Nanotechnology, Silver, Surface area

168

We report an enhancement in the efficiency of organic solar cells via the incorporation of gold (Au) or silver (Ag) nanoparticles (NPs) in the hole-transporting buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which was formed on an indium tin oxide (ITO) surface by the spin-coating of PEDOT:PSS-Au or Ag NPs composite solution. The composite solution was synthesized by a simple in situ preparation method which involved the reduction of chloroauric acid (HAuCl4) or silver nitrate (AgNO3) with sodium borohydride (NaBH4) solution in the presence of aqueous PEDOT:PSS media. The NPs were well dispersed in the PEDOT:PSS media and showed a characteristic absorption peak due to the surface plasmon resonance effect. Organic solar cells with the structure of ITO/PEDOT:PSS-Au, Ag NPs/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM)/LiF/Al exhibited an 8% improvement in their power conversion efficiency mainly due to the enlarged surface roughness of the PEDOT:PSS, which lead to an improvement in the charge collection and ultimately improvements in the short-circuit current density and fill factor.

Concepts: Gold, Lithium aluminium hydride, Solar cell, Indium tin oxide, Energy conversion, Silver, Surface plasmon resonance, PEDOT:PSS

148

Silver nanoparticle (Ag NP)-loaded chitosan composites have numerous biomedical applications; however, fabricating uniform composite microparticles remains challenging. This paper presents a novel microfluidic approach for single-step and in situ synthesis of Ag NP-loaded chitosan microparticles. This proposed approach enables obtaining uniform and monodisperse Ag NP-loaded chitosan microparticles measuring several hundred micrometers. In addition, the diameter of the composites can be tuned by adjusting the flow on the microfluidic chip. The composite particles containing Ag NPs were characterized using UV-vis spectra and scanning electron microscopy-energy dispersive X-ray spectrometry data. The characteristic peaks of Ag NPs in the UV-vis spectra and the element mapping or pattern revealed the formation of nanosized silver particles. The results of antibacterial tests indicated that both chitosan and composite particles showed antibacterial ability, and Ag NPs could enhance the inhibition rate and exhibited dose-dependent antibacterial ability. Because of the properties of Ag NPs and chitosan, the synthesized composite microparticles can be used in several future potential applications, such as bactericidal agents for water disinfection, antipathogens, and surface plasma resonance enhancers.

Concepts: Synthesis, Composite material, Silver, In situ, Microfluidics, Composite video, Aramid, Kevlar

139

Silver nanoparticles were green synthesized with the aqueous leaf extract of the widely consumed green leafy vegetable, Rumex acetosa (sorrel) and the obtained silver nanoparticles (Ag NPs) were tested for their in vitro antioxidant potential, cytotoxicity against human osteosarcoma (HOS) cell lines and antibacterial effects against sixteen human pathogenic clinical isolates. Different analytical techniques viz. UV-vis, FTIR, XRD, SEM-EDX and TEM were employed to characterize the synthesized Ag NPs. Surface Plasmon spectra for the Ag NPs with brownish black color were centered approximately at 448 nm. FTIR analysis revealed the presence of reactive N-H and O-H groups that are effective in reducing Ag(I) ions to Ag(0) which then reacted with the contents of the extract to AgCl/Ag2C2O4. From SEM and TEM analyses, the particles were found to be predominantly spherical in shape and ranged in size from 5 nm to 80 nm, but were largely in the range of 15 nm to 20 nm. Ag NPs showed considerable antioxidant activity, and all the sixteen clinical isolates of human pathogens tested were significantly inhibited. Also, HOS cell lines were significantly (p < 0.05) inhibited at 25% concentration of the Ag NPs extract, while showing a marginal revival at 50% and 100% concentrations.

Concepts: Cell, Bacteria, Concentration, Pathogen, Silver, Leaf, Leaf vegetable, Rumex

84

Silver (Ag) is one of the seven metals of antiquity and an important engineering material in the electronic, medical, and chemical industries because of its unique noble and catalytic properties. Ag thin films are extensively used in modern electronics primarily because of their oxidation-resistance. Here we report a novel phenomenon of Ag nano-volcanic eruption that is caused by interactions between Ag and oxygen (O). It involves grain boundary liquation, the ejection of transient Ag-O fluids through grain boundaries, and the decomposition of Ag-O fluids into O2 gas and suspended Ag and Ag2O clusters. Subsequent coating with re-deposited Ag-O and the de-alloying of O yield a conformal amorphous Ag coating. Patterned Ag hillock arrays and direct Ag-to-Ag bonding can be formed by the homogenous crystallization of amorphous coatings. The Ag “nano-volcanic eruption” mechanism is elaborated, shedding light on a new mechanism of hillock formation and new applications of amorphous Ag coatings.

Concepts: Oxygen, Crystallography, Hydrogen, Nitrogen, Chemical element, Materials science, Silver, Chemical industry

81

The ability to pattern planar and freestanding 3D metallic architectures at the microscale would enable myriad applications, including flexible electronics, displays, sensors, and electrically small antennas. A 3D printing method is introduced that combines direct ink writing with a focused laser that locally anneals printed metallic features “on-the-fly.” To optimize the nozzle-to-laser separation distance, the heat transfer along the printed silver wire is modeled as a function of printing speed, laser intensity, and pulse duration. Laser-assisted direct ink writing is used to pattern highly conductive, ductile metallic interconnects, springs, and freestanding spiral architectures on flexible and rigid substrates.

Concepts: Electricity, Heat, Aluminium, Metal, Copper, Silver, Printing, Inkjet printer

48

Microparticles containing substantial amounts of radiocesium collected from the ground in Fukushima were investigated mainly by transmission electron microscopy (TEM) and X-ray microanalysis with scanning TEM (STEM). Particles of around 2 μm in diameter are basically silicate glass containing Fe and Zn as transition metals, Cs, Rb and K as alkali ions, and Sn as substantial elements. These elements are homogeneously distributed in the glass except Cs which has a concentration gradient, increasing from center to surface. Nano-sized crystallites such as copper- zinc- and molybdenum sulfide, and silver telluride were found inside the microparticles, which probably resulted from the segregation of the silicate and sulfide (telluride) during molten-stage. An alkali-depleted layer of ca. 0.2 μm thick exists at the outer side of the particle collected from cedar leaves 8 months after the nuclear accident, suggesting gradual leaching of radiocesium from the microparticles in the natural environment.

Concepts: Electron, Iron, Chernobyl disaster, Uranium, Zinc, Copper, Silver, Transition metal

43

Conformational changes of Aβ peptide result in its transformation from native monomeric state to the toxic soluble dimers, oligomers and insoluble aggregates that are hallmarks of Alzheimer’s disease (AD). Interactions of zinc ions with Aβ are mediated by the N-terminal Aβ1-16 domain and appear to play a key role in AD progression. There is a range of results indicating that these interactions trigger the Aβ plaque formation. We have determined structure and functional characteristics of the metal binding domains derived from several Aβ variants and found that their zinc-induced oligomerization is governed by conformational changes in the minimal zinc binding site 6HDSGYEVHH14. The residue H6 and segment 11EVHH14, which are part of this site are crucial for formation of the two zinc-mediated interaction interfaces in Aβ. These structural determinants can be considered as promising targets for rational design of the AD-modifying drugs aimed at blocking pathological Aβ aggregation.

Concepts: Alzheimer's disease, Proteins, Protein, Peptide, Aluminium, Monomer, Silver, Oligomer

37

Throughout Antiquity magical amulets written on papyri, lead and silver were used for apotropaic reasons. While papyri often can be unrolled and deciphered, metal scrolls, usually very thin and tightly rolled up, cannot easily be unrolled without damaging the metal. This leaves us with unreadable results due to the damage done or with the decision not to unroll the scroll. The texts vary greatly and tell us about the cultural environment and local as well as individual practices at a variety of locations across the Mediterranean. Here we present the methodology and the results of the digital unfolding of a silver sheet from Jerash in Jordan from the mid-8(th) century CE. The scroll was inscribed with 17 lines in presumed pseudo-Arabic as well as some magical signs. The successful unfolding shows that it is possible to digitally unfold complexly folded scrolls, but that it requires a combination of the know-how of the software and linguistic knowledge.

Concepts: Epistemology, Linguistics, Writing, Silver, Jordan, Torah, Codex, Scroll

34

Questions about how to regulate nano-enhanced products regularly arise as researchers determine possible nanoparticle transformation(s). Focusing concern on the incorporation and subsequent release of nano-Ag in the fabrics often overshadows the fact that many “conventional silver” antimicrobials such as ionic silver, AgCl, metallic Ag and other forms will also form different species of silver. In this study we used a laboratory washing machine to simulate the household laundering of a number of textiles prepared with known conventional Ag or nano-Ag treatments and a commercially available fabric incorporating yarns coated with bulk metallic Ag. Serial filtration allowed for quantification of total Ag released in various size fractions (> 0.45 µm, < 0.45 µm, < 0.1 µm and < 10 kDa) while characterization of particles with TEM/EDX provided insight on Ag transformation mechanisms. Most conventional Ag-additives yielded more total Ag and more nano-particulate sized Ag in washing liquid than fabrics that used nano-Ag treatments. Incorporating the nanosilver into the fiber (opposed to surface treatments) yielded less total Ag during fabric washing. A variety of metallic Ag, AgCl, and Ag/S particles were observed in washing solution by TEM/EDX to various extents depending on the initial Ag speciation in the fabrics. Very similar particles were also observed when dissolved ionic Ag was added directly into the washing liquid. Based on the present study, we can state that all silver-treated textiles, regardless if the treatment is "conventional" or "nano", can be a source of silver nanoparticles in washing solution when laundering fabrics. Indeed, in this study we observed that textiles treated with "conventional" silver have equal or greater propensity to form nano-silver particles during washing conditions than those treated with "nano" silver. This fact needs to be strongly considered when addressing the risks of nano-silver and emphasizes that regulatory assessment of nanosilver warrants a similar approach to conventional silver.

Concepts: Nanoparticle, Nanotechnology, Nanomaterials, Sol-gel, Colloid, Silver, Textile, Silver Nano