Silver Foil Research Articles

Energy level alignment and interface states at α-sexithiophene/Ag interfaces

We present a combined X-ray and ultraviolet photoemission study of the interface between the thiophene based organic semiconductor α-sexithiophene (6T) and silver. Thermally evaporated organic films were deposited in several steps without breaking the vacuum on polycrystalline silver foils. Subsequently, the films were characterized via photoemission spectroscopy. These series of spectra allowed the determination of the energy level alignment at the interface. Our results provide evidence that chemical interaction takes place between flat lying α-6T molecules and the silver surface resulting in interface electronic levels. From the observed well defined molecular orbitals we have analyzed the energy level alignment and have found an interface dipole of −0.7 eV and a hole injection barrier of about 1.8 eV.

Generation of electromagnetic waves by nonrelativistic charged particle interaction with metal surfaces

In this paper, different aspects of transition radiation generation in optical and SHF ranges have been experimentally studied. UV luminescence induced by nonrelativistic protons passing through silver foil was measured at different incident angles. Luminescence continuous light spectrum has one maximum near 326nm. It corresponds to the wavelength of silver volume plasmon excitation. The origin of light generation in this wavelength band is discussed.Besides, we describe our experimental results on SHF electromagnetic radiation generation produced by nonrelativistic electron bunches passing through diaphragms of various geometries. The results are in a good agreement with predictions of transition radiation theory for nonrelativistic charged particles passing through apertured conducting screens.

Template assisted solid state electrochemical growth of silver micro- and nanowires

We report on a template based solid state electrochemical method for fabricating silver nanowires with predefined diameter, depending only on the pore diameter of the template. As templates we used porous silicon with pore diameters in the μm range and porous alumina with pore diameters in the nm range. The template pores were filled with silver sulfide (a mixed silver cation and electronic conductor) by direct chemical reaction of silver and sulfur. The filled template was then placed between a silver foil as anode (bottom side) and a microelectrode (top side) as cathode. An array of small cylindrical transference cells with diameters in the range of either micro- or nanometers was thus obtained. By applying a cathodic voltage to the microelectrode silver in the form of either micro- or nanowires was deposited at about 150 °C. The growth rate is controllable by the electric current.

Ag–Al based air braze for high temperature electrochemical devices

Silver–aluminum based air brazing was attempted using an in situ alloying and brazing process. In this process, layers of foils of aluminum and silver were laid up between alumina plates in alternating fashion to achieve three target compositions representing Ag, Ag 3Al, and Ag 2Al phases. Each alloy composition revealed different microstructure, mechanical properties and fracture mechanisms. Joints brazed with foils containing 9.8 at% Al formed a long continuous layer parallel to the direction of the original aluminum foil. The fracture occurred at low bend strength (6–12 MPa) mainly through the interface between this newly formed long alumina layer and the braze filler. Joints containing 26.5 at% Al in the braze filler metal experienced the series of phase transformations, leading to cracks in as-brazed specimens. The fracture initiated through these pre-existing cracks, thus the joint strength observed in these specimens was extremely low. The joints prepared using foils with 35.1 at% Al exhibited a good interface even though interfacial alumina particles formed during air brazing. Crack propagation occurred along the interface between the alumina substrate and in situ formed interfacial alumina particles or directly through these particles. Due to the good interface, the best bend strength (46–52 MPa) was achieved for the braze filler containing 35 at% Al.

Surface-enhanced Raman spectroscopy and density functional theory study on 4,4′-bipyridine molecule

The molecular geometry and vibrational frequencies of 4,4′-bipyridine (BPE) in the ground state were calculated using density functional theory (DFT) methods (B3LYP) with 6-31++G(d,p) basis set. The optimized geometric bond lengths and bond angles are obtained by DFT employing the hybrid of Beckes non-local three parameter exchange and correlation functional and Lee–Yang–Parr correlation functional. Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and near-infrared surface-enhanced Raman scattering (NIR-SERS) spectra of BPE on the silver foil substrate have been recorded. All FT-IR, FT-Raman and NIR-SERS band were assigned on the basis of the B3LYP/6-31++G(d,p) method. The vibrational frequencies obtained by DFT(3LYP) are in good agreement with observed results. The NIR-SERS of BPE excited by 1064 nm laser line is little difference with that excited by visible laser line. This phenomenon is result to the increase of the contribution of CHEM enhancement effect. Surface selection rules derived from the electromagnetic enhancement model were employed to infer the orientations of BPE on the silver foil substrate surface. Some vibrational frequency which are sensitive to the planar or non-planar structure of BPE, and to the dihedral angle were concluded.

Structure, morphology, and composition of nanometric Pd films deposited by dc magnetron sputtering on Cu, Ag, and Au foils

The comprehension of atomic and electronic structures of bimetallic systems is important in several areas, such as catalysis, sensors, and microelectronics. The aim of this study is to investigate thin (10 nm) films of palladium deposited on polycrystalline copper, silver, and gold foils by dc magnetron sputtering. We employed atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) in order to characterize the morphology, structure, and surface composition of the films. AFM images revealed that the surfaces of Cu and, in a smaller degree, Ag foils were covered with small grains (particles). XPS results indicated that these particles were oxidized copper and silver. Gold substrate presented a flat morphology, with no detectable oxide formation. Pd films covered the small particles for both Cu and Ag substrates, presenting a flat morphology. In the case of Pd film deposited on Au, the morphology was similar to the substrate. For all three cases, XPS results indicated that Pd is mainly in the metallic state. XRD results showed the presence of a polycrystalline Pd film on top of Cu foil, but not for either Ag or Au foils.

EFFECTS OF COLORED MULCHES ON “B” SIZE POTATOES

The small, B size potatoes (<2 inches but ≥1.25 inches in diameter) represent a keen interest in new, specialty food items. Exotic shapes and color shades of the specialty varieties are also known for intense flavors and variations in textures in firmness and fiber that consumers are looking for today in an ever increasing health consciousness among consumers. In 2006, the varieties `French Fingerling' (West Edmonton, Alberta, Canada), Villetta Rose (Univ. of Wisconsin) and B1145-2 (USDA, Beltsville, Md.) were planted in a double row 8 inches between tubers and 18 inches between rows in a replicated trial using colored mulches. The mulch color included red, white, black, blue, green, and silver foil. These plastic mulches were laid on 6-ft centers. The mulches were shown to affect the microclimate of soil temperature, as expected, and therefore affecting yield. These temperature differences were measured with a Campbell CR 10X weather station (Logan, Utah) probes at a 2 inches above the soil surface and 4 and 6 inches below the soil surface. Plant stands were excellent with all mulches, however, blue mulch caused early emergence while white and silver delayed emergence. Just the opposite effect happened when it came to yields. The highest individual tubers per plant came from the white mulch with the green having the lowest tuber yields. Cultivar differences were also seen in there ability to produce marketable tubers. `Villetta Rose' had the highest plant vigor and also the most marketable tubers per plant. B1145-2 produced most of its tubers >2 inches in diameter with the tubers nonuniform in shape. French Fingerling produced a very uniform oblong tuber with few defects. Yields and quality were above normal for all cultivars when grown on either the silver reflective mulch or the white mulch.

Density functional theory calculation of vibrational spectroscopy of trans-1,2-bis(4-pyridyl)-ethylene

The molecular geometry and vibrational frequencies of trans-1,2-bis(4-pyridyl)-ethylene ( t-BPE) in the ground state were calculated using density functional theory (DFT) methods with 6–31++G(2d,p) basis set. The optimized geometric bond lengths and bond angles are obtained by DFT employing the hybrid of Beckes nonlocal three-parameter exchange and correlation functional and Lee–Yang–Parr correlation functional (B3LYP). Fourier transform Infrared (FTIR), Fourier transform Raman (FT-Raman) and near-infrared surface-enhanced Raman scattering (NIR-SERS) spectra of t-BPE on the silver foil substrate were recorded. All FTIR, FT-Raman and NIR-SERS band were assigned on the basis of the B3LYP/6-31++G(2d,p) method. The vibrational frequencies obtained by DFT(B3LYP) are in good agreement with observed results. Surface selection rules derived from the electromagnetic enhancement model were employed to infer the orientations of t-BPE on the silver foil substrate surface.

Spectroscopy of 4,4′-azopyridine by density functional theory and surface-enhanced Raman scattering

The molecular geometry and vibrational frequencies of 4,4′-azopyridine (AZPY) were calculated using the density functional theory (DFT) methods. Fourier transform infrared (FTIR), fourier transform Raman (FT-Raman) and near-infrared surface-enhanced Raman scattering (NIR-SERS) spectra of AZPY on the silver foil substrate have been recorded. On the basis of the computed results, FTIR, FT-Raman and NIR-SERS bands were assigned. It is shown that the calculated and observed frequencies are in good agreement with each other for FTIR and FT-Raman spectra. Surface selection rules derived from the electromagnetic enhancement model were employed to infer the orientations of AZPY on the silver foil substrate surface.

Microchemical investigation of Greek and Roman silver and gold plated coins: coating techniques and corrosion mechanisms

Within the framework of a project financially supported by the European Commission (contract Nr. 509126, acronym PROMET) the metallurgical techniques used by Romans and Greeks for coating the copper core of coins with a thin or thick layer of gold or silver are studied by means of the combined use of scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS) and optical microscopy (OM) techniques. This approach is utilised to gain further insight into the micro-chemical structure of the external regions of the coins as well as into the bulk metallurgical features. The results indicate that several methods were used by the Greek and Roman craftsmen including the mechanical application of a thin malleable gold or silver foils to be welded via thermal treatment. The analytical approach is also used for investigating the corrosion products grown on the coins during the long-term burial and for identifying degradation mechanisms.

Silver jewelry of Hellenistic and Celtic type from Hrtkovci in Srem

Group find of the silver jewelry of the Hellenistic and Celtic type has been discovered by chance in the area of the Hrtkovci village. The find consists of gilded hinged fibula, three fibulae of the Middle La T?ne type and many pendants made of thin silver foil. Most of the finds are dated in the 2nd-1st century BC and only the new type of hinged fibula dates from considerably earlier period, possibly from the end of 4th or the beginning of the 3rd century BC. The new finds of silver jewelry discovered in the area of eastern Srem and dating from the Pre-Roman times confirm the existence of the local workshop connected most probably to the Pre-Roman fortified settlement in Sremska Mitrovica.

Justifying the need to prescribe limits for toxic metal contaminants in food-grade silver foils

The use of silver foils in various food preparations is a common practice in Middle Eastern and South East Asian countries. The FAO/WHO Joint Expert Committee on Food Additives (JECFA) has included silver in the list of food additives, but specifications were not prepared. Indian food legislation has included food-grade silver foil and laid down a purity requirement of 99.9%. This leaves an unspecified margin of 0.1% or 1000 µg g−1 for contaminants. Therefore, a study to investigate the levels of metallic contaminants in food-grade silver foil was undertaken. Of 178 foils analysed, 161 (90%) contained silver, whilst 10% were fraudulently made up of aluminium. In the case of silver foils, 46% of the samples adhered to the desired purity requirement of 99.9%, while 54% had a lower silver content. Copper was present in 86.3% of the silver foils, while chromium, nickel and lead contamination was found in over 54% of samples. Cadmium levels were detected in 28% of the silver foils and manganese was present in 6.8% of samples. In silver foils showing metal contaminants, average levels were found for nickel (487 µg g−1), lead (301 µg g−1), copper (324 µg g−1), chromium (83 µg g−1), cadmium (97 µg g−1) and manganese (43 µg g−1), which being appreciable justify the need to prescribe limits for some metals in food-grade silver foil as well as for silver powder used in confectioneries and medicinal preparations. The work reported here should encourage manufacturers to use high-purity raw materials and take suitable precautions to reduce unwarranted exposure of consumers to toxic metal contaminants.

Enigmas of bidri

Metal surfaces of objet d’art were usually kept highly polished in the past and chemical patination as a decorative technique was rare before the 19th century. The best known exceptions are the Japanese irogane alloys and their occidental precursors. Another less well known patinated metal are the bidri wares of India. The items are sand castings of an alloy containing ∼95% of zinc and 5% of copper. After casting the pieces are heavily inlaid with silver wires and foils and then treated to produce a rich black patina. Bidri wares are still made in quantity in the Deccan of central India, including at Bidar in the state of Karnataka, the traditional centre of the industry from which bidri takes its name. Zinc metal was first prepared in India ∼1000 years ago and so an association between zinc production and zinc artefacts seems natural. However, this is not really the case, and the origins are really quite mysterious. Bidri has always been made in the Moslem parts of India by Moslem craftsmen who claim that the technique began in the Middle East, but where there was no zinc. Zinc was produced only at Zawar in the Hindu Rajput states of Rajasthan, well over 1000 km from the nearest bidri maker, and furthermore the few lead isotope analyses performed on the early bidri wares show the zinc did not come from Zawar. Thus the origins of the technique and the source of the zinc are shrouded in mystery, and a further mystery concerns the chemical nature of the patinated layer itself. None of the minerals identified in the patinated layer by X-ray diffraction should be black, but clearly some form of finely divided and probably amorphous copper oxide must be responsible. Whatever its origins and composition, bidri wares continue to be made and to provide a quintessential craft product of India.

Influence of growth conditions and weak fields on the electrical properties of the vortex and superconducting states of Bi 2Sr 2CaCu 2O x thick tapes

A systematic investigation of the electrical parameters of Bi 2Sr 2CaCu 2O x thick tapes in the vortex and superconducting states was carried out. The tapes were grown on either single crystals of MgO or silver foil under different heat treatment conditions. The temperature dependence of the electrical resistivity in the vortex state was found to follow an Arrhenius-like relation of the form ρ( T, H) = ρ 0exp(− U 0( H)/ k B T). The activation energy, U 0, showed a strong dependence on the applied field and the growth conditions of the sample. Its average values were between 10 and 300 meV. The current–voltage characteristics ( I– V) for various samples of different growth conditions and applied fields were also investigated. The study revealed a current dependence on the applied voltage was found to fit a power law of the form: I ∼ V α , where α is an exponent whose values are strongly dependent on growth conditions. At constant voltages, the current was found to decrease exponentially with the applied magnetic field according to I( B) ∼ exp(− cB/ B ∗), where c is a constant depending on growth conditions and B ∗ is a characteristic field of the sample. This exponential decay of the current is attributed to strong flux pinning centers. The dependence of the current on field and voltage could be written as I ∼ V α exp(− cB/ B ∗). Furthermore, the heat treatment conditions and annealing atmosphere had strong influence on the I– V characteristic of the sample.

EFFECTS OF COLORED MULCHES ON “B” SIZE POTATOES

The small, “B” size potatoes (<2 inches but ≥1.25 inches in diameter) represent a keen interest in new, specialty food items. Exotic shapes and color shades of the specialty varieties are also known for intense flavors and variations in textures in firmness and fiber that consumers are looking for today in an ever increasing health consciousness among consumers. In 2004, the varieties `French Fingerling' (West Edmonton, Alberta, Canada), W2275-3R (Univ. of Wisconsin) and B1145-2 (USDA, Beltsville, Maryland) were planted in a double row 8 inches between tubers and 18 inches between rows in a replicated trial using colored mulches. The mulch color included red, white, black, blue, green, and silver foil. These plastic mulches were laid on 6-ft centers. The mulches were shown to affect the microclimate of soil temperature, as expected, and therefore affecting yield. These temperature differences were measured with a Campbell CR 10X weather station (Logan, Utah) probes at 2 inches above the soil surface and 4 and 6 inches below the soil surface. Plant stands were excellent with all mulches, however, blue mulch caused early emergence while white and silver delayed emergence. Just the opposite effect happened when it came to yields. The highest individual tubers per plant came from the silver mulch with the blue having the lowest tuber yields. Cultivar differences were also seen in there ability to produce marketable tubers. `French Fingerling' had the highest plant vigor and also the most marketable tubers per plant. B1145-2 produced most of its tubers greater than 2 inches in diameter with the tubers nonuniform in shape. W2275-3R produced a very uniform round tuber with few defects. Yields were higher this past year, however, there was a greater incidence of hollow heart due to excess water and higher fertility.

Analysis of nucleotides and oligonucleotides immobilized as self-assembled monolayers by static secondary ion mass spectrometry.

Nucleic acid constituents can be bound to a metal surface in the form of self-assembled monolayers. Binding is achieved either through ionic interactions with a self-assembled 2-aminoethanethiol monolayer or by direct covalent binding of a dithiophosphate oligonucleotide to a metal surface through a sulfur-metal bond. Nucleotides, polynucleotides (both normal and a dithiophosphate analog) and double-stranded DNA have all been bound to surfaces. When the surfaces are interrogated using static secondary ion mass spectrometry (SIMS), the surface-bound nucleic acid constituents are observed in the form of the characteristic protonated nucleic acid base ions (BH2+). While a silver foil substrate was found to provide the highest absolute signal, vapor-deposited gold yields the best signal-to-noise ratio for ionically bound deoxyguanosine monophosphate. Under comparable conditions, a Cs+ projectile produces a 10-fold increase in the secondary ion signal relative to a Ga+ projectile. The experiment has been extended to a triple-quadrupole instrument where tandem mass spectrometric experiments on ionically immobilized dGMP showed the characteristic loss of ammonia from the released BH2+ ion. When a 'biomimetic' surface formed by ionically immobilizing double-stranded DNA is exposed to a solution containing ethidium bromide, ions corresponding to the non-covalent adduct are readily detectable using SIMS. This adduct and the nucleic acid constituents can be monitored at levels below 10 fmol.

Laser-based synthesis of core Ag-shell AgI nanoparticles

A laser-controlled synthesis of silver iodide (AgI) nanoparticles with isolable AgI shell–Ag core stable intermediates is achieved via molecular iodine photodissociation in the presence of pure Ag nanoparticles dispersed in water. Ag nanoparticles were introduced into the solution containing sodium dodecylsulphate surfactants and iodine by ablating a piece of silver foil with a 532 nm pulsed Nd-YAG laser. Transmission electron microscopy images showed that different AgI shell–Ag core sizes could be achieved by controlling the photolysis of I 2 in solution. These nanoparticles were also found to catalyse an atom-economy Grignard–Barbier organic reaction.

Les pots de médicament de Yakushi Bouddha (bouddha de la guérison) au Japon

The origin of Yakushi buddha (Bhaisajyaguru in Sanscrit, buddha of healing) is not clearly known. It has been proposed the original statue of Yakushi buddha may have been conceived from Varna, a god in Brahminism, believed to be a god of justice who possessed medicines and prolonged life. It is believed that Yakushi buddha appeared in Japan when the buddhism was imported from Korea and China in VI century, Yakushi buddha was believed more profoundly in Japan, compared with Korea and China.The reasons are probably as follows: Yakushi buddha is buddha of healing, Emperor Temmu (672-685) built Yakushi-ji temple in Nara, Emperor Shomu (724-749) built Kokubun-ji temples at principal towns. The principal statues of buddha in these temples are Yakushi buddha. In Japan, there are 252 Yakushi Buddha statues in Buddhistical Temples, which are listed in Important Cultural Property including 14 National Treasures. Belief in Yakushi Buddha was especially prevalent from the 7th to the 13th centuries in Japan. The oldest wooden Yakushi Buddha statue is in the Horin-ji temple in Nara. Among the 252 Yakushi Buddha statues, 224 are in wood, 15 are in copper, 6 are in picture and etc. 212 (84,1%) have medicinal pots (or rarely, a bowl) on the palm of left hand. However, these medicinal containers are wooden blocks. Very recently, it was found that Yakushi Buddha statue in the Suho-Kokubun-ji temple (Yamaguchi Prefecture, Japan) has a medicinal pot on the palm of the left hand in which an offering (220 g materials) was found. The date on the reverse side of lid places the offering at October 12, 1699. The offering is composed of five cereals (rice, barley, wheat, soybean, adzuki bean), five medicinal plants (Acori Graminei, Acori Calami, Radix Ginseng, Flos Caryophylli, Lignum Santali Albi), and five minerals (rock crystals, purple and blue glasse, CaCO3, particles, silver and golden foils). DNA analysis proved those three randomly selected seeds of rice all belongs to the template japonica, which is predominant in the present variety of Japan.

In Vivo Multitracer Analysis Technique: Screening of Radioactive Probes for Noninvasive Measurement of Physiological Functions in Experimental Animals

A novel screening experiment, to find radioactive probes for non-invasive measurements of physiological functions in experimental animals, was tested using the in vivo multitracer analysis technique. The details of the efficiency of the detector settings used in the in vivo multitracer analysis technique were examined by both computer simulations and practical measurements. Multiple radioactive isotopes, i.e. multitracer, were prepared by irradiating a silver foil target with a heavy ion beam at the RIKEN ring cyclotron. After chemical separation of the silver target, the multitracer was finally dissolved in isotonic citrate buffer. The multitracer solution was intravenously injected into rats. Using a gamma-ray detector equipped with a well-defined slit, the collimated gamma-rays from the upper abdomen of living rats were measured. After correction of detection efficiencies, it was possible to compare the distribution of radioactive elements between two groups of rats different in body weight. The in vivo measurement showed that the tissue substantial volume of the selenium-deficient (SeD) rat liver increased compared to normal rats. The possibility of a functional estimation of tissue/blood volume for living rats was proposed based on the characteristic in vivo distribution of 74As, 83Rb and 103Ru.

Role of phosphates in the promotion of silver catalysts for partial oxidation: I. Structure and properties of phosphates on the surface of polycrystalline silver

The chemical composition, structure, and properties of an H3PO4-promoted polycrystalline silver foil are studied by XPS. The surface of the doped sample contains oxygen in two states with binding energies of 531.1 and 533.0 eV. Heat treatment results in silver clusters distributed in the polyphosphate matrix. It follows from TDS data that the surface of the promoted catalyst contains a strongly bound oxygen species that desorbs at ~900 K. It is believed that the silver clusters stabilized by the phosphate matrix are active sites on the surface of the phosphorus-promoted catalyst.