Trace Amounts Of Ag Research Articles

Bithiophene-based COFs for silver ions detection and removal

Covalent organic frameworks (COFs) are promising in the detection and removal of toxic heavy metal ions from water. However, achieving detection and removal functions requires systematic control of stability, porosity, pore environment, and luminescence properties, which remains a challenge for most COFs materials. Herein, we develop a bithiophene-based stable COF, TAPA-BTDC, with dual functions of simultaneous detection and removal of silver ions from aqueous solution through elaborate structural design and control of the pore environment. The obtained TAPA-BTDC has good thermal stability and chemical stability, possesses high crystallinity and moderate specific surface area (396.83 m2/g), and contains dense bithiophene-S chelating sites on the pore walls. These characteristics work together to give TAPA-BTDC the dual function of selective detection and effective removal of silver ions from aqueous solution. This dual function can be attributed to the π-complexation between bithiophene-S chelating sites and silver ions, as verified by X-ray photoelectron spectroscopy. The charge transfer between bithiophene-S and silver ions alters the weak fluorescence emission caused by the π−π layered structure, enabling TAPA-BTDC to selectively detect silver ions through fluorescence enhancement, and even trace amounts of Ag+ (2.4 × 10−4 mmol/L) can cause observable fluorescence emission. Meanwhile, these bithiophene-S scattered across the pore wall also provide a large number of accessible chelating sites for TAPA-BTDC, enabling it to effectively remove Ag+ with a maximum adsorption capacity up to 398.61 mg/g, and TAPA-BTDC can be easily regenerated five times without loss of performance. The results of this study reveal the exceptional potential of COFs with reasonably tailor-made structure in dealing with heavy metal ion contamination.

Distribution Patterns of Ag in Hydrothermal Precipitates from the Okinawa Trough

AbstractThe Okinawa Trough is characterized by enrichment of Ag in hydrothermal precipitates; however, the distribution of this enrichment remains poorly constrained. This study presents the results of a field‐emission scanning electron microscopy and electron‐microprobe analysis based mineralogical and geochemical investigation of the spatial distribution of Ag within Ag‐rich sulfide samples from the Okinawa Trough. The tetrahedrite, covellite, and galena in these samples contain high concentrations of Ag (average values of 1.60, 0.78, and 0.23 wt%, respectively) and also various Ag sulfosalts. Examination of the Ag budget of these samples indicates that most of the Ag is hosted by tetrahedrite followed by galena. The Ag within tetrahedrite is incorporated by substitution into the Cu site, whereas galena becomes Ag‐enriched by the coupled incorporation of monovalent Ag, Tl, and Cu, and trivalent Sb and Bi into Pb lattice sites. Tetrahedrite and galena containing higher concentrations of Sb favor increased Ag substitution. Four sets of Ag host minerals are identified with distinct ore formation temperatures. Tetrahedrite and galena concentrate the majority of Ag at medium temperatures (150–300°C). Other Ag host minerals concentrate only minor or trace amounts of Ag, including massive sphalerite, chalcopyrite, and pyrite at high temperatures (>300°C), colloform pyrite and sphalerite at low temperatures (<150°C), and Ag‐sulfosalts at even lower temperatures (<100°C).

Polyimide Metallization Using Nickel Nano-Film as both Catalyst and Barrier Layer of Copper Electroless Deposition

Polyimide (PI) metallization using Ni-nanofilm (Ni-nF) as the copper barrier layer and catalyst layer of electroless copper deposition was carried out. The surface of the PI film was hydrolyzed by KOH to form a layer of poly-amic acid (PAA) and subsequently performed ion-exchange of K+ ions with Ni2+ ions. The doped Ni2+ ions can be rapidly chemically reduced to the dense and continuous Ni-nF, if the reducing solution [i.e., dimethylamine borane (DMAB)] contained a trace amount of Ag+, Cu2+ or Pd2+ ions. To characterize the materials and propose a mechanism of Ni-nF formation, Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and secondary ion mass spectrometer (SIMS) were employed in this work. The main reason of Ni-nF formation is caused by a high concentration gradient of doped Ni2+ ions in the PAA that results from the addition of those metallic ions in the DMAB solution.

Influence of a Trace Alloying of Ag on the Ageing Behavior and Mechanical Properties of AZ80M Magnesium Alloys

The ageing behavior of AZ80+xAg (x=0;0.3;0.5) magnesium alloys at different temperature were systematically investigated using optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Experimental results demonstrate that the trace amount of Ag accelerated the precipitation of Mg17Al12 phase during ageing at 200°C, AZ80+0.5Ag achieved the peak hardness of 89.7HV after holding for 12h, compared with 80.8HV after 28h for the Ag-free alloy. However, when ageing at high temperature (250°C), the promotion response of Ag was totally vanished. The tensile property of the peak aged alloys at ambient temperature increased with Ag addition, as well as the tensile property at elevated temperature. Further investigation indicates that Ag addition suppresses the discontinuous precipitates, which account for the enhanced property of Ag-containing alloy.

The rapid age strengthening induced by Ag additions in 7075 aluminum alloy

The trace amount of Ag (0.4wt% Ag) addition can remarkably accelerate the precipitation (the aging time reduced by 50%) in 7075 Al alloy, and the strength of the alloy with 0.4wt% Ag is also improved, which is attributed to the large amount of Mg–Ag clusters.

A Novel Disinfection Material-Nano Ag Particle Impregnated Media

In this study, the nano-silver impregnated media (NAg-ball) was proposed to inactive E. coli in water. After 24 h of contact with NAg-ball, about 99 % removal of E. coli from the water sample with an initial bacteria loading oItalic textf 103 - 105 CFU/ml was observed. According 32 day repetitive use, periodical surface cleaning would be suggested to maintain the high inactivation lasting of NAg-ball. The dosing of 1: 20 (Nag-ball: water) was found to be the best and most suitable in a 500 L pilot scale. This result confirmed the existence of synergistic effect lower dose shall be expected to treat the same loading of bacteria for further larger scale. Toxicity Characteristic Leaching Procedure (TCLP) test revealed trace amount of Ag, Cu, Cr and Zn released from NAg-ball into the treated water sample. In conclusion, nano-silver impregnated media has very good inactivation performance on E. coli. This NAg-ball provides a safe, convenient and effective solution in drinking water treatment, especially in the mountain area.

Comparative study of carbon paste electrodes modified by new pentaaza macrocyclic ligands and gold nanoparticles embedded in three-dimensional sol–gel network for determination of trace amounts of Ag(I)

Two new Ag(I) chemically modified carbon paste electrodes were prepared with comparative potentiometric study of 1,3,6,10,13-pentaaza-2,14-(2,6-pyridyl)-cyclotetradecane-4,12-dione (PPCT) and 1,3,6,9,11,12-pentaaza-2,13-(2,6-pyridyle)-bicycle[2,2,9]pentadecane-4,11-dione (PPBP) as ionophore. These sensors have been modified with sol–gel–Au nanoparticles to obtain a wide concentration range for potentiometric determination of Ag(I) in aqueous solutions. The sensors exhibit significantly enhanced selectivity toward Ag(I) ions over a wide concentration range of 4.0 × 10−9–2.2 × 10−2 and 2.2 × 10−7–2.0 × 10−2 mol L−1 with a lower detection limit of 2.5 × 10−9 and 2.0 × 10−7 mol L−1 for PPCT and PPBP modified electrodes respectively. The electrodes are highly selective to Ag(I) ions over a large number of mono, bi, and tri-valent cations. These electrodes were successfully used as indicator electrode for potentiometric determination of silver in sulphadiazine (burning cream) and radiological film.

PETROGRAPHY, CHEMISTRY, AND NEAR-INFRARED MICROTHERMOMETRY OF INDIUM-BEARING SPHALERITE FROM THE TOYOHA POLYMETALLIC DEPOSIT, JAPAN

Textural, chemical, and microthermometric characteristics of In-bearing sphalerite from the Toyoha Zn-Pb-Ag-Cu-Sn-In vein-type deposit are investigated using petrography, X-ray mapping, electron microprobe analyses, and near-infrared (NIR) microscopy. The studied ore is rich in zinc and mainly consists of sphalerite. The In-bearing sphalerite formed as euhedral growth bandings after corrosion of In-free sphalerite and replacement of a precursor mineral. The In-bearing sphalerite, which appears black and dark red in thin sections, is zoned with alternating high and low In bands. This zoning is only visible by X-ray mapping. There is a positive correlation between In and Cu, supporting the case for coupled substitution: In3+ + Cu+ 2 Zn2+. The maximum concentrations of In and Cu in sphalerite are 7.03 and 3.65 wt %, respectively. Indium is also commonly correlated with trace amounts of Ag and Sn. Primary fluid inclusions suggest that the maximum formation temperature of In-bearing sphalerite is 305°C. This indicates that In concentration in Zn-rich ores occurred at lower temperatures than in Cu-rich In-bearing ores (350°–400°C) previously reported at Toyoha. Textural and chemical characteristics indicate that fluids enriched in In, Cu, Ag, and Sn formed In-bearing sphalerite after corrosion of In-free sphalerite and replacement of a precursor mineral. Combined with previous geological, mineralogical, and experimental studies, we propose that In was transported by high-temperature (≥300°C) fluids enriched in In, Cu, Ag, and Sn. Indium may have been derived by remobilization of the metals from the preexisting Cu-rich ores at depth and/or injection of metal-rich fluid from a new source.

Anodic stripping voltammetric determination of silver(I) in water using a 4-tert-butyl-1(ethoxycarbonylmethoxy)thiacalix[4]arene modified glassy carbon electrode

A glassy carbon electrode coated with film of 4-tert-butyl-1-(ethoxycarbonylmethoxy)thiacalix[4]arene is designed for the determination of trace amounts of Ag+. Compared with bare glassy carbon electrode, the modified electrode can greatly improve the measuring sensitivity for Ag+. Under the optimum experimental conditions, the modified electrode in B-R buffer solution (pH 4.5) shows a linear voltammetric response in the range of 5.0 × 10−8–3.0 × 10−6 M with detection limit 1.0 × 10−8 M for Ag+. The high sensitivity, selectivity, and stability of modified electrode also demonstrate its practical application for a simple, rapid and economical determination of Ag+ in water samples.

Effects of Trace Elements in Copper Fillers on the Electrical Properties of Conductive Adhesives

The properties of electrically conductive adhesives (ECAs) filled with Cu and Cu alloy fillers (with alloy elements Ag, Ge, Mg, and Zn) were investigated in terms of electrical conductivity, thermal stability, and the effects of the trace alloy elements on the oxidation resistance of the metallic fillers. Oxidation of metallic fillers under high-temperature exposure at 125°C was considered as the main reason that led to degradation of electrical conductivity in the ECAs. Cu fillers alloyed with a trace amount of Ag and Mg, respectively, had significant effects on the electrical conductivity and thermal stability of the ECAs as the electrical resistivity was substantially suppressed and a consistently high electrical conductivity could be maintained even after aging for 1000 h at 125°C.

Microstructure and mechanical properties of Al–Cu–Mg–Mn–Zr alloy with trace amounts of Ag

The microstructure and mechanical properties of Al–Cu–Mg–(Ag)–Mn–Zr alloys were studied by means of tensile testing, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that small additions of Ag to Al–Cu–Mg–Mn–Zr alloy can accelerate the hardening effect of the aged alloy and reduce the time to peak-aged. The mechanical properties can be improved both at room temperature and at elevated temperatures, which is attributed to the fine and uniform plate-like Ω precipitates. Meanwhile the ductility of the studied alloys remains at relatively high level. The major strengthening phases of the Ag-free alloy are θ′ and less S′, while that of Al–Cu–Mg–Mn–Zr alloy containing trace amounts of Ag are Ω and less θ′.

Synthesis of novel chitosan resin possessing histidine moiety and its application to the determination of trace silver by ICP-AES coupled with triplet automated-pretreatment system

A novel chitosan resin, cross-linked chitosan functionalized with histidine moiety (histidine-type chitosan resin), was synthesized for the collection and concentration of trace silver in aquatic samples. A triplet automated-pretreatment system (Triplet Auto-Pret System) installed mini-columns packed with the synthesized histidine-type chitosan resin was coupled with an inductively coupled plasma-atomic emission spectrometry (ICP-AES) for a rapid and sensitive analysis. Adsorption behavior of 50 elements on the histidine-type chitosan resin was examined. A trace amount of Ag(I) was shown a good adsorption in wide pH regions (pH 5–9), and Ag(I) adsorbed was readily recovered with 1 M nitric acid solution. The limit of detection (3 σ) for silver was 0.03 μg L −1. The system was successfully applied to river water and dipped water in silver coated container.

Modified BINOL Podands: Synthesis of Dinaphthosulfide Podands and Their Application in Spectrophotometric Determination of Toxic Metals

New dinaphthosulfide podands [3(a, b, and c)] were synthesized. The structures of these compounds were confirmed by IR, 1H NMR, 13C NMR, and Mass spectra. A simple, efficient, and sensitive procedure is described for the spectrophotometric determination of a trace amount of Ag+, Hg2+, Cr3+, Pb2+, and Ni2+ cations in the presence of Mn2+, Co2+, Cd2+ cations using the podand (3a). Formation constants of 1:1 complexes were determined from the absorbance-mole ratio data and found to vary in the order Pb2+ > Ni2+ > Hg2+ > Cr3+ > Ag+.

Ion-exchange studies of 110mAg(I) using synthetic inorganic ion-exchanger

In the present investigation, the selective adsorption of silver on synthetic inorganic ion exchanger, zinc(II) ferrocyanide, has been established by batch method, under specific conditions, using 110mAg as a tracer. The efficiency of adsorption has been determined by γ-ray spectrometry and was found to be greater than 96%. The Ag(I) uptake by the exchanger has also been evaluated. The selectivity of the method was checked by studying the adsorption of Ag(I) in the presence of a number of foreign ions using their corresponding tracers. The interfering ions were removed by washing the ion-exchanger with appropriate reagents, so that it could be applied for the determination of trace amount of Ag(I) in complex matrices, containing trace amount of other metal ions.

Selective Flotation‐Separation and Inductively Coupled Plasma‐Atomic Emission Spectrometric Determination of Ultra Trace Amounts of Silver Ion Using Bis(2‐mercaptoanil)acetylacetone

A rapid, selective and highly sensitive flotation method is developed for separation and enrichment of ultra trace amounts of Ag+ ion from water samples. At pH 6.0 and using sodium dodecylsulfate as a foaming agent, Ag+ was separated with bis(2‐mercaptoanil)acetylacetone (BMAA) added to 1000 mL of aqueous solution. The proposed procedure of pre‐concentration is applied prior to the determination of silver ion using inductively coupled plasma‐atomic emission spectrometry (ICP‐AES). The influences of pH, concentration of BMAA, applicability of different surfactants and foreign ions on the separation efficiency were investigated. The pre‐concentration factor of the method is 1000 and the detection limit is 0.045 µg mL−1.

Highly selective cloud point extraction and preconcentration of trace amounts of silver in water samples using synthesized Schiff’s base followed by flame atomic absorption spectrometric determination

A simple and useful method employing cloud point extraction is proposed for the preconcentration and separation of silver in water samples. The silver cation reacts with bis(2-mercaptoanil) acetylacetone (BMAA) at pH 6. The resulting compound is subsequently entrapped in the Triton X-114 micelles. After optimization of the complexation and extraction conditions, a preconcentration factor of 50 was obtained (volume of initial sample was 10 mL). As an analytical example, trace amounts of Ag were determined, after preconcentration, in a complex aqueous matrix such as seawater using flame atomic absorption spectrometry. The calibration curve was linear in the range 2–200 ng/mL and the limit of detection was 0.43 ng/mL. The relative standard deviation was lower than 2.4%.

Stability of silver thin films on cobalt and nickel silicides

Silver thin films were deposited on cobalt and nickel silicides to evaluate the thermal stability of the films during vacuum annealing. Rutherford backscattering spectrometry of annealed films revealed film changes to occur at 700 °C. Scanning electron microscopy of annealed films shows grain coarsening of the Ag film with increasing anneal temperature. At 650 °C, tears appear in the film. Increasing temperature up to 700 °C agglomerates the film. X-ray diffraction glancing angle scans revealed no phase changes in annealed films. Scans from the as-deposited case and the 700 °C, both show the same reflection peaks being present. Secondary ion mass spectroscopy depth profiling revealed trace amounts of Ag at the silicide/silicon interface following a heat treatment. This occurrence appears to be temperature independent. Equal amounts of Ag were discovered at the silicide interface for all samples annealed from 450 up to 700 °C.

Catalytic Kinetic Spectrophotometric Determination of Trace Amounts of Silver in Triton X-100 Micellar Medium

A catalytic method has been developed for the determination of trace amounts of Ag+ in Triton X-100 micellar medium. The method is based on the catalytic effect of silver(I) on the rate of a ligand substitution reaction between potassium ferrocyanide and 4,7-biphenyl-1,10-phenanthroline (BPT). The reaction was followed spectrophotometrically at 536 nm by measuring the induction period. Beer's law was obeyed in the range of 0–0.040 µg/mL Ag+ and the apparent molar absorptivity was 2.43 × 106 L mol−1 cm−1. Both the influence of reaction variables and the interference of coexistent ions were studied. The proposed method has been applied to the wastewater samples with satisfactory results. The recoveries were between 93.2 and 107% and the RSD was below 4.0%.

Kinetic–Spectrophotometric Determination of Trace Silver(I) Using Its Catalytic Effect on the Oxidation Reaction of Fuchsin by Peroxodisulfate in the Presence of 1,10-Phenanthroline As an Activator

A kinetic spectrophotometric method for the determination of trace amounts of Ag(I) in the range of 2–20 ng mL–1 is reported. The method is based on the catalytic effect of Ag(I) on the oxidation reaction of fuschin by potassium peroxodisulfate in the presence of 1,10-phenanthroline as an activator at pH = 5. The reaction is followed spectrophotometrically by measuring the change in absorbance (ΔA) at 544 nm using a fixed time method (6 min). The reaction variables were optimized in order to achieve the highest sensitivity. The 3s criterion detection limit was 0.7 ng mL–1, and the relative standard deviation for ten replicate measurements of 16 ng mL–1 of Ag(I) was 0.95% (n = 10). The method was successfully applied to the determination of silver in expired black and white photographic films and results showed good agreements with those obtained by atomic absorption spectrometry.

Evidence of noble metal diffusion in polymers at room temperature and its retardation by a chromium barrier

Recent applications of organic low-k dielectrics in microelectronics have stimulated many investigations of metal diffusion in polymers. Here we report results from radiotracer measurements of110mAg diffusion in trimethylcyclohexane polycarbonate. Serial sectioning was carried out with 190 eV krypton ions in and opposite to the diffusion direction to rule out sputtering artifacts. Ag was found to be strongly immobilized by self aggregation. In contrast to earlier reports, however, trace amounts of Ag were clearly seen to diffuse into the polymer even at room temperature. A chromium film of only one tenth of a monolayer turned out to be an effective diffusion barrier.