Search results for "SILVER"
showing 10 items of 697 documents
Some aspects of formation and tribological properties of silver nanodumbbells.
2013
In this paper, metal nanodumbbells (NDs) formed by laser-induced melting of Ag nanowires (NWs) on an oxidized silicon substrate and their tribological properties are investigated. The mechanism of ND formation is proposed and illustrated with finite element method simulations. Tribological measurements consist in controllable real-time manipulation of NDs inside a scanning electron microscope (SEM) with simultaneous force registration. The geometry of NDs enables to distinguish between different types of motion, i.e. rolling, sliding and rotation. Real contact areas are calculated from the traces left after the displacement of NDs and compared to the contact areas predicted by the contact m…
Modeling Corrosion of Archaeological Silver-Copper Coins Using the Voltammetry of Immobilized Particles
2012
Two complementary models to describe the long-term corrosion of silver-copper coins, based on potential rate laws for smooth corrosion and those combined with diffusive law, for gross corrosion, are proposed. Theoretical kinetics can be tested using signatures of copper and silver corrosion products using the voltammetry of immobilized particles technique. The method is applied to silver coins minted during the 13th–14th centuries from the Libertad street hoard in Valencia (Spain) using non-invasive one-touch graphite pencil sampling. Voltammetric features yield functional dependences in agreement with the proposed model potentially useful for distinguishing between different mints.
Highly Sensitive plasmonic silver nanorods
2011
We compare the single-particle plasmonic sensitivity of silver and gold nanorods with similar resonance wavelengths by monitoring the plasmon resonance shift upon changing the environment from water to 12.5% sucrose solution. We find that silver nanoparticles have 1.2 to 2 times higher sensitivity than gold, in good agreement with simulations based on the boundary-elements-method (BEM). To exclude the effect of particle volume on sensitivity, we test gold rods with increasing particle width at a given resonance wavelength. Using the Drude-model of optical properties of metals together with the quasi-static approximation (QSA) for localized surface plasmons, we show that the dominant contrib…
System Design Rules for Intensifying the Electrochemical Reduction of CO 2 to CO on Ag Nanoparticles
2020
Electroreduction of CO2 (eCO2RR) is a potentially sustainable approach for carbon-based chemical production. Despite significant progress, performing eCO2RR economically at scale is challenging. Here we report meeting key technoeconomic benchmarks simultaneously through electrolyte engineering and process optimization. A systematic flow electrolysis study - performing eCO2RR to CO on Ag nanoparticles as a function of electrolyte composition (cations, anions), electrolyte concentration, electrolyte flow rate, cathode catalyst loading, and CO2 flow rate - resulted in partial current densities of 417 and 866 mA/cm2 with faradaic efficiencies of 100 and 98 % at cell potentials of −2.5 and −3.0 …
(Ag)Pd-Fe3O4 Nanocomposites as Novel Catalysts for Methane Partial Oxidation at Low Temperature
2020
Nanostructured composite materials based on noble mono-(Pd) or bi-metallic (Ag/Pd) particles supported on mixed iron oxides (II/III) with bulk magnetite structure (Fe3O4) have been developed in order to assess their potential for heterogeneous catalysis applications in methane partial oxidation. Advancing the direct transformation of methane into value-added chemicals is consensually accepted as the key to ensuring sustainable development in the forthcoming future. On the one hand, nanosized Fe3O4 particles with spherical morphology were synthesized by an aqueous-based reflux method employing different Fe (II)/Fe (III) molar ratios (2 or 4) and reflux temperatures (80, 95 or 110 °
Chromosomal location polymorphism of major rDNA sites in two Mediterranean populations of the killifih Aphanius fasciatus (Pisces: Cyprinodontidae)
2005
The chromosomes of the Mediterranean killifish, Aphanius fasciatus from two populations, the Lagoon of Venice (LV, 15 specimens) and the Lagoon ‘Stagnone di Marsala’ (Sicily) (SM, 48 specimens), have been investigated using conventional Ag-staining and fluorescent in situ hybridization (FISH) with 18S rDNA probe. The two methods revealed variation in the number of major rDNA sites ranging from 8 to 14 (LV) and from 1 to 4 (SM) per individual. The fact that each individual possessed its own number of sites implies that observed variation was structural. Moreover, overlapping of silver staining and FISH patterns demonstrated that all ribosomal genes were transcriptionally active in each speci…
Bipyridine based metallogels: an unprecedented difference in photochemical and chemical reduction in the in situ nanoparticle formation
2017
Metal co-ordination induced supramolecular gelation of low molecular weight organic ligands is a rapidly expanding area of research due to the potential in creating hierarchically self-assembled multi-stimuli responsive materials. In this context, structurally simple O-methylpyridine derivatives of 4,4′-dihydroxy-2,2′-bipyridine ligands are reported. Upon complexation with Ag(I) ions in aqueous dimethyl sulfoxide (DMSO) solutions the ligands spontaneously form metallosupramolecular gels at concentrations as low as 0.6 w/v%. The metal ions induce the self-assembly of three dimensional (3D) fibrillar networks followed by the spontaneous in situ reduction of the Ag-centers to silver nanopartic…
Analysis of cell proliferation rate in Oral Leukoplakia and Oral Squamous Cell Carcinoma
2010
Objectives: Assessment of the cell proliferation rate in tissues can be one of the markers for impending malignancy in precancers. The state of activation and the proliferation activity of the cells can be assessed by the frequency of silver stained Nucleolar Organiser regions (AgNOR) within the nuclei which is significantly higher in malignant cells. The present study was carried out to analyze the distribution of the AgNOR in oral leukoplakia (OL) and oral squamous cell carcinoma (OSCC), and in their various histological grades, and to assess if the AgNOR distribution could give information on the malignant potentiality in premalignant lesions and aggressiveness of the malignant lesions. …
An Intermetallic Au24Ag20 Superatom Nanocluster Stabilized by Labile Ligands
2015
An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L …
Effect of silver diamine fluoride on the bond durability of normal and carious dentin
2019
Background Silver diamine fluoride (SDF) has attracted attention because of its clinical success in arresting dentin caries. It has been shown that it can inhibit matrix metalloproteinases and cysteine cathepsins. These two properties might be beneficial in bonding to caries-affected dentin (CAD). Therefore, the present study aimed to investigate the effect of SDF on the durability and bond strength to the CAD. Material and Methods Forty-eight third molars with occlusal caries were used. The roots were cut, and the occlusal enamel was removed. The CAD area surrounded by the normal dentin (ND) was exposed. All the specimens were bonded with an etch-and-rinse adhesive, but half of them were t…