Ions Of Ag Research Articles

Diffusion Mechanism of Ag ions in Superionic Conductor Ag2Se from Ab Initio Molecular-Dynamics Simulations

The dynamic properties of mobile Ag ions in the superionic conductor Ag 2 Se are studied by ab initio molecular-dynamics simulations. The population analysis including the gross charge and the overlap population shows that the bonding properties of Ag ions change accompanied with the diffusive motion. By investigating the displacement-correlation functions between Ag ions, it is clarified that Ag ions exhibit a collective motion with their neighbor Ag ions when they migrate between neighboring tetrahedral sites.

Function of Silver in the Mixed ITE Activators for Lead-acid Batteries

The behaviors of Ag+ and activator were studied on Pb anode for lead-acid batteries. The deposition of Ag and dissolution of Ag+ take place at lower potential than redox couple of Pb/PbSO4. This process may be considered to activate the reaction in the redox couple of Pb/PbSO4. The activator molecules are less adsorbable on bear Pb, and adsorbed easily on PbSO4 formed on Pb. The complex ions of Ag+ and activator molecule are adsorbable on bear Pb, and PbSO4 is initially formed on the adsorbed layer of complex ions.

Gamma Ray-induced Reduction and Removal of Heavy Metal Ions in Aqueous Solutions

Possibility of reduction and removal of heavy metal ions Ag+, Zn2+, Cu2+, and Co2+ from water by irradiation of γ ray was investigated. No concentration change was found when aqueous solutions of the metal ions were irradiated with γ ray either directly, or after bubbling with He gas. On the other hand, the metal ions were reduced to lower oxidation states by the irradiation in the presence of Na2SO3. Precipitates were observed in all the irradiated solutions of 4 metal ions of Ag+, Zn2+, Cu2+, and Co2+. Ag+ was found to be reduced to metallic Ag.

Characterization of Ag+-Exchanged Zeolite A with H2 and CO Adsorption by FTIR

Abstract The reversible reduction–oxidation processes of Ag+ ions in Ag+-exchanged zeolites A (AgA) with H2 and O2 adsorption were studied by Fourier transform infrared (FTIR) spectroscopy. CO adsorption was carried out at low temperature to probe the functional groups present on AgA (before and after H2 adsorption) and their locations in the channels of zeolite. The hydroxy groups were formed upon H2 (D2) adsorption on AgA with different IR frequencies depending on the degree of Ag+-exchange. It was found that these generated hydroxy groups mainly locate inside the β-cages in AgA at 30%-exchange degree, as evidenced by the inaccessibility of CO due to the small six-oxygen ring windows. On the contrary, the hydroxy groups, which had already been formed before H2 adsorption due to the dissociation of H2O on Ag+ ions, could interact with CO, showing an IR band at 2156 cm−1. This indicates that of hydroxy groups of this type are situated inside the larger α-cages containing 8-membered rings or on the external surface. The CO stretching band of CO–Na+ adducts appeared at 2165 cm−1 and could be easily removed by evacuation, while the CO–Ag+ species was detected at 2182 cm−1 and was highly resistant toward evacuation even at ambient temperature.

Curvature-based residual stress measurement for ion-implanted stainless-steel sheet

Residual stress in ion-implanted stainless-steel sheet and the effects of ion species and implantation dose on the residual stress were investigated by using curvature technique based on the Stoney equation. Six species of ions of Au, Ag, Fe, Ni, Ti and Si were implanted into the stainless steel sheet with an energy of 3 MeV at the dose of 1.0×10 16 to 10 17 ions/ cm 2 . The depth profile of the ion implantation in the ion-implanted layer was examined by using transmission electron microscopy equipped with an energy-dispersive X-ray spectroscopy. The level of the residual stress evaluated by the Stoney equation was compared with the results of X-ray diffraction.

Paramagnetic susceptibility simulations from crystal field effects on Nd3+ in AgNd(WO4)2

Polycrystalline AgNd(WO4)2 has been prepared by a in solid-state reaction. X-ray diffraction measurements indicate that this compound crystallizes with a scheelite-type tetragonal structure. Absorption and emission spectra have been measured, using the technique of the crystal field parameters, to obtain the energy levels scheme for Nd3+ ions in the crystalline matrix. These data indicate the existence of a structural local disorder associated with a random distribution of the ions of Ag+ and Nd3+. The temperature variation of the paramagnetic susceptibility in the range from 2 to 300 K has been studied. The Van Vleck formula has been used to calculate the temperature variation of the paramagnetic susceptibility and it was compared with the experimental results. Particularly at low temperatures, satisfactory agreement has been obtained.

Adsorption of metal ions on humic acids extracted from brown coals

The paper shows results of examination of ion exchange capacity of solid and gel forms of humic acids of brown coals in respect to 17 metal ions. Adsorption of metal ions from single- and multicomponent solutions was carried out in dynamical conditions. The highest affinity to active centers of humic acids proved to have ions of Pb, Ag, Hg, Cu, Ba and Cd. Both types of humic acids selectively adsorbed lead ions, whereas gel forms of humic acids were selective adsorbers of Cr +3 and Al +3. Examination of IR spectra showed that the higher pH solutions, the higher share of the COOH groups in metal ions bonding was involved. The Pb, Ag, Hg and Cu ions are exceptional because even at low pH reaction of the solution (<5) they are bounded with phenolic groups as well. Only these metal ions are able to form complex compounds with carboxylic and phenolic groups of humic acids.

Effect of subtoxic concentrations of metal ions on NFkappaB activation in THP-1 human monocytes.

THP-1 human monocytes and human peripheral blood monocytes have altered inflammatory cytokine secretion profiles after exposure to a variety of metal ions known to be released from biomaterials. Transcriptional regulation of these cytokines often involves activation of the transcription factor NFkappaB. The present study was designed to determine whether metal ion treatment of monocytes results in changes in levels of activated NFkappaB. THP-1 cells were grown in suspension in the presence of sublethal concentrations of ions of Ag(+), Co(2+), Cu(2+), Hg(2+), Ni(2+), and Pd(2+). After 24 h of exposure to metal ions, the cells were harvested, counted, and the nuclear proteins extracted. Electrophoretic mobility shift assays were performed using a (32)P-ATP end-labeled oligonucleotide consensus sequence for the NFkappaB transcription factor. DNA/protein complexes were quantified by phosphorimage analysis and compared by ANOVA (Tukey, alpha = 0.05). Exposure of THP-1 cells to 100 microM of Pd(2+) caused a significant increase in activated NFkappaB (p < 0.05) whereas treatment with 5 microM of Ag(+) resulted in significantly decreased levels of nuclear NFkappaB (p < 0.05). No other metal ions tested caused a significant change in basal levels of nuclear NFkappaB (Co(2+), Hg(2+), Ni(2+), and Cu(2+)). However, exposure to 50 microM of Cu(2+) resulted in a reproducible, though not significant, increase in nuclear NFkappaB levels. These results indicate that inflammatory responses to some metal ions may be influenced by NFkappaB-mediated transcriptional regulation.

ToF-SIMS characterization of molecular ions from Fomblin Z-DOL on Ag substrates

There is great difficulty to obtain molecular ions from the lubricant actually as films on magnetic recording disks. With the assistance of Ag cationization, quasi-molecular ions of (Ag+M) + from Fomblin Z-DOL cast on Ag substrate were successfully observed on the positive time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra. Considering the mass interference between oligomers, detailed distributions of molecular weight ( M n) and monomer ratio ( m/ n) could be extracted. The average values of M n and m/ n obtained by ToF-SIMS are in good agreement with other conventional technique such as nuclear magnetic resonance spectroscopy (NMR).

Purification and characterization of hydrolase with chitinase and chitosanase activity from commercial stem bromelain.

A hydrolase with chitinase and chitosanase activity was purified from commercial stem bromelain through sequential steps of SP-Sepharose ion-exchange adsorption, HiLoad Superdex 75 gel filtration, HiLoad Q Sepharose ion-exchange chromatography, and Superdex 75 HR gel filtration. The purified hydrolase was homogeneous, as examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme exhibited chitinase activity for hydrolysis of glycol chitin and 4-methylumbelliferyl beta-D-N,N',N' '-triacetylchitotrioside [4-MU-beta-(GlcNAc)(3)] and chitosanase activity for chitosan hydrolysis. For glycol chitin hydrolysis, the enzyme had an optimal pH of 4, an optimal temperature of 60 degrees C, and a K(m) of 0.2 mg/mL. For the 4-MU-beta-(GlcNAc)(3) hydrolysis, the enzyme had an optimal pH of 4 and an optimal temperature of 50 degrees C. For the chitosan hydrolysis, the enzyme had an optimal pH of 3, an optimal temperature of 50 degrees C, and a K(m) of 0.88 mg/mL. For hydrolysis of chitosans with various N-acetyl contents, the enzyme degraded 30-80% deacetylated chitosan most effectively. The enzyme split chitin or chitosan in an endo-manner. The molecular mass of the enzyme estimated by gel filtration was 31.4 kDa, and the isoelectric point estimated by isoelectric focusing electrophoresis was 5.9. Heavy metal ions of Hg(2+) and Ag(+), p-hydroxymercuribenzoic acid, and N-bromosuccinimide significantly inhibited the enzyme activity.

Identification of Defects in Undoped Semi-insulating InPby Positron Lifetime

Positron lifetime measurements, carried out over the temperature rangeof 10-300 K, have been used to investigate defects in two undopedsemi-insulating InP samples. The positron lifetime spectra wereanalysed by both PATFIT and MELT techniques. The results at roomtemperature reveal a positron lifetime of around 273 ps, which isassociated with indium vacancies VIn or VIn-hydrogencomplexes. The positron average lifetime is temperature dependent anddecreases with increasing temperature at the beginning (⩽80 K and⩽120 K), and then remains unchanged, which is attributed to theinfluence of negative vacancies and detrapping of the positron fromthose negative ions of Mg, Zn, Ag and Ca with ionization level (1-).

Purification and Characterization of Alkaline Proteinase from AlkalophilicBacillussp.

Alkaline proteinase was purified from Bacillussp. isolated from soil. The pH optimum was 11.5 at 37°C. Calcium divalent cation was effective in stabilizing the enzyme, especially at higher temperatures. The proteolytic activity was inhibited by the specific serine proteinase inhibitor PMSF (phenylmethylsulfonyl fluoride), and ions of Mg, Mn, Pb, Li, Zn, Ag, and Hg. The enzyme was stable in the presence of detergents, such as Triton-X100, Tween-80, SDS (sodium dodecyl sulfate), and EDTA (ethylenediaminetetraacetic acid), at pH 11.5 and 37°C for 30 min. The optimum pH was 11.5 at 37°C, and the optimum temperature was 62°C at pH 11.5.

Noble metal ion sorption by pyridyl and bipyridyl group-containing chelating polymers

A series of eighteen 4-vinylpyridine and 4-methyl-4′-vinylbipyridine copolymers with different crosslinkers was examined as sorbents for the noble metal ions of Ag(I), Au(III), Pd(II), and Pt(II) from aqueous solutions. The chelating polymers possess appreciable sorption selectivity for Au(III) over Ag(I) and for Pd(II) over Pt(II). Binding abilities of the copolymers toward the noble metal ions vary as the identity of the chelating heterocyclic amine moiety and the structure of the crosslinkers are altered. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 207–213, 2001

Soil-modified carbon paste electrode: a useful tool in environmental assessment of heavy metal ion binding interactions.

Carbon paste electrodes (CPEs) modified with different soils in their native form were prepared to create a soil-like solid phase suitable for application in studies of heavy metal ion uptake and binding interactions. The preparation of CPEs modified with five different soils was examined and their heavy metal ion uptake behavior investigated using a model Cu(II) aqueous solution. Metal ions were accumulated under open circuit conditions and were determined after a medium exchange using differential pulse anodic stripping voltammetry, applying preelectrolysis at -0.7 V. The soil-modified CPE accumulation behavior, including the linearity of the current response versus Cu(II) concentration, the influence of the pH on the solution, and the uptake kinetics, was thoroughly investigated. The correlation between the soil-modified CPE uptake capability and the standard soil parameters, such as ion exchange capacity, soil pH, organic matter and clay content, were evaluated for all five examined soils. The influence of selected endogenous cations (K(I), Ca(II), Fe(III)) on the transfer of Cu(II) ions from a solution to the simulated soil solid phase was examined and is discussed. Preliminary examinations of the soil-modified CPE uptake behavior with some exogenous heavy metal ions of strong environmental interest (Pb(II), Hg(II), Cd(II) and Ag(I)) are also presented. This work demonstrates some attractive possibilities for the application of a soil-modified CPE in studying soil-heavy metal ion binding interactions, with a further potential use as a new environmental sensor appropriate for fist on-site testing of polluted soils.

Colors of Ag+-Exchanged Zeolite A

UV/vis spectra of hydrated and activated Ag+xNa+12-xA, Ag+xCa2+6-0.5xA, and Ag+9.5ZK-4 materials were studied. Any absorption band or color observed in silver zeolite A materials is due to the presence of silver ions. The marked site preference of ions in Ag+xCa2+6-0.5xA was found to offer the unique possibility of investigating different coordination sites of Ag+ ions in zeolite A. Observations we made lead to the result that Ag+ coordinated to 6- and 8-ring oxygens gives rise to electronic transitions in the near-UV region. Only Ag+ coordinated to 4-ring oxygens leads to the 22 000 cm-1 absorption responsible for the typical deep yellow color. The red color which is caused by a strong absorption band at 19 000 cm-1 is observed if a 4-ring coordinated Ag+ has a second Ag+ as a neighbor. We assume that the second Ag+ is at a 6-ring site. Yellow and red colored materials turn colorless again when exposed to humidity. The reversibility is complete for the yellow samples while a broad but weak absorption in the near-UV remains after rehydration of the red samples. Molecular orbital calculations were carried out on a unit structure cell consisting of 1296 atoms. The occupied frontier orbital region consists mainly of two bunches of levels: the HOMO region which spreads from about −11 to − 12.6 eV and the next lower lying levels below −13.6 eV. The HOMO region consists of oxygen lone pairs O(n). We find that 6-ring coordinated Ag+ gives rise to near-UV electronic transitions and 4-ring coordinated Ag+ causes a band in the visible. These transitions can be interpreted as charge transfer from zeolite oxygen lone pairs to Ag+. We therefore denote them as Ag+(5s) ← O(n) LMCT.

An experimental study of stopping power for MeV heavy ions

A 60 MeV Ag primary ion beam was used to generate secondary recoil ion beams of Cl, K, Ca, Sc, Ti, V, Mn and Cu in the energy range 0.1-0.6 MeV . The stopping power in the carbon absorber was measured and compared with Lindhard, Scharff and Schiott (LSS) theory, the Northcliffe and Schilling model and semiempirical estimates of Ziegler et al (1985). Data for heavier ions of Ag, I and Au from other sources was also considered in order to extend the scope of such a comparison. LSS theory was found to satisfy the data within a narrow mid-velocity range (-, where is Bohr velocity). Estimates made by Ziegler et al were seen to generally agree to within a few per cent except for energies below 0.2 MeV , where deviations as high as 25% were seen. Expected oscillations could not be discerned down to the lowest ion velocities so far attempted.

Mobility of Silver Ions in Silver Ion Conductor Ag7NbS6 Studied by Ag and Nb NMR

Temperature dependences of the 109Ag chemical shift and the spin−lattice relaxation time, T1, of 109Ag, 107Ag, and 93Nb NMR have been measured in the room-temperature phase of Ag7NbS6 and related compounds. The 109Ag chemical shift is about 1300 ppm and is much larger than those of other silver compounds. The 109Ag and 107Ag line widths are about 200 Hz, and these indicate that the motional narrowing of silver ions has been completed in this phase. T1 of all nuclei increases with increasing temperature. The relaxationl process is explainable by the fluctuations of scalar coupling between silver nuclei, because the T1 of 109Ag does not show any magnetic field dependence. The temperature dependences of T1 of the mobile 109Ag and 107Ag are weaker than that of T1 of the immobile 93Nb as well found in the case of Ag9GaSe6. Though Ag7NbS6 and related compounds show a high ionic conductivity of 0.1−1 S m-1, high affinity between the silver and chalcogenides and correlation among silver ions are suggested by the ...

Electronic stopping powers of Au, Ag, Cu, Pd and Co metals for 19F ions at low velocity

Electronic stopping cross sections for 80–350 keV 19F ions in Au, Ag, Cu, Pd and Co films were obtained by range measurement. Depth profiles of 19F in these materials were measured by 19F( p, αγ) 16O resonance nuclear reaction. A proper deconvolution program was used to extract the depth distribution parameters from the experimental excitation yield curves. The electronic stopping powers were derived through fitting the projected ranges simulated by TRIM/XLL code to the experimentally determined projected ranges. It is shown that the electronic stopping cross sections obtained in this work agree well with those calculated by using TRIM96 as well as previous experimental data and can be described by the four-parameter formulae.

A model of oxide layer growth on Ag + and Pt + ion implanted nickel anode in aqueous alkaline solution

This work investigates nickel oxide films growth on implanted with ions of the noble metals Ag and Pt. Polycrystalline and single crystal samples of Ni were implanted with high fluences (1 × 10 19 – 1 × 10 21 m −2 of 9–50 keV ions. Galvanostatic and potentiostatic polarization techniques were applied to monitor the electrochemical efficiencies of formation of Ni x O 1− x films in aqueous KOH solution (30%) at 353 K. The growth rates, thickness and compositional profiles of oxidised nickel layers were examined by means of RBS. It was found that the anodic oxide film consists of Ni(OH) 2 XH 2O ( X ≥ 1). Anodic oxidation of nickel occurs due to out-diffusion of Ni atoms through the hydroxide layer. Implanted Ag penetrates partly into the anodic oxide whereas platinum is completely buried beneath the oxide film.

木質材料 ケイ酸塩を用いた木材の無機質複合化 （第７報） コロイダルシリカ溶液による木材の無機質複合化とその性質

The applicability of colloidal silica for producing a wood-mineral composite by impregnation was investigated, and its properties such as dimensional stability and decay and fire resistances were evaluated.The colloidal silica solution was prepared by mixing silicic acid anhydride (30.4%), boric acid, and chitosan with a low molecular weight (0.3%). Instead of boric acid, metal ions of Cu, Ag, or Ti (1000ppm) were added to the solution. The solution was diffusion-penetrated into the water-saturated specimens of Sugi (Cryptomeria japonica D. Don), followed by drying to solidify the colloidal silica for a combination. The formation of silicic acid gel in the composites made by using the colloidal silica solution system was proved to be mostly insoluble.The composites showed an antiswelling efficiency with the greatest value of 23% due to the bulking effect despite being hygroscopic and a good reduction in water absorptivity. Also, the composites, particularly those by using the colloidal silica-boric acid system, were found to improve greatly the decay and fire resistances.For practical use, the composites were manufactured with boards of yellow poplar (Liriodendron tulipifera L.) applying the colloidal silica-boric acid system. They showed the enhancement of bending strength and modulus of elasticity to some extent of apparent weight percent gains. The absorbed energy in impact bending became greater than that of the untreated wood.