High Silver Content Research Articles

Behavioural effects on marine amphipods exposed to silver ions and silver nanoparticles

Behavioural responses to contaminants are an important endpoint in ecotoxicology because they link effects at biochemical or cellular levels to impacts on individual fitness. Due to the increasing use of silver in nanomaterials, studies of its effects on the behaviour of aquatic organisms are important to assess the risks of silver nanoparticles (AgNP) released into the environment. The aim of this work was to evaluate the behavioural effects of silver on the marine amphipod Echinogammarus marinus after exposure to AgNO3 via water and AgCl or AgNP via food. Swimming activity of the amphipods was tracked during 6 min alternating dark and light conditions. Animals swam slower and responded less to light at higher concentrations of silver in the water. No differences were found in the behaviour of animals exposed via feeding up to 28 days, hence, longer exposure times may be required for the observation of effects. This is the first work to appraise behaviour effects of silver ions and AgNP on marine amphipods. Although the protocol has been successfully developed for this purpose, specimens appeared to habituate to test conditions during the experiments. Therefore, the need for further understanding of baseline behaviours in these model organisms is discussed.

Argentous Deep Eutectic Solvent Approach for Scaling Up the Production of Colloidal Silver Nanocrystals

Conventional colloidal nanocrystal synthesis is conducted in batch formats which produce materials on a scale far below what is required for industrial applications. As a practical solution to this challenge, we show herein that a task-specific argentous deep eutectic solvent (DES) comprising a 1:4 mixture of silver triflate with acetamide can be used as a fluidic metal precursor to push the production of silver nanocrystals to large quantities. This approach employs oleylamine as cosolvent, reductant, and colloid capping agent and is shown to quickly produce large amounts of high-quality monodispersed silver nanocrystals (AgNCs) in a simple microwave-mediated reduction (2 min reaction at 200 °C). The large initial silver concentration ([Ag]0) of the DES-based reaction medium in turn allows a high colloidal concentration of AgNCs to be accomplished. For an [Ag]0 of 0.50 M, the highest silver concentration which gave uniform AgNCs a colloidal concentration of 54 mg mL–1 was attained, equivalent to the prod...

Fabrication of the large-area flexible transparent heaters using electric-field-driven jet deposition micro-scale 3D printing

Abstract In order to realize the mass production of the large-area flexible transparent film heater (FTFH) at low-cost, this paper presents a novel method which can achieve the direct fabrication of the large-area FTFH with Ag-grid by using an electric-field-driven jet deposition micro-scale 3D printing. The effects of the line width and the pitch of the printed Ag-grids on the optical transmittance and the sheet resistance are revealed. A typical FTFH with area of 80 mm × 60 mm, optical transmittance of 91.5% and sheet resistance of 4.7 Ω sq−1 is fabricated by the nano-silver paste with a high silver content (80 wt.%) and high viscosity (up to 20 000 mPa · s). Temperature-time response profiles and heating temperature distribution show that the heating performance of the FTFH has good thermal and mechanical properties. Furthermore, the adhesive force grade between the Ag-grid and the PET substrate measured to be 4B by 3M scotch tape. Therefore, the FTFH fabricated here is expected to be widely used in industry, such as window defroster of vehicles and display or touch screens owing to its striking characteristics of large area and low cost fabrication.

Microstructure and mechanical properties of Sn–1.0Ag–0.5Cu solder with minor Zn additions

Low silver (Ag) solder alloys e.g., SAC 105 (Sn–1.0Ag–0.5Cu) have attracted a great deal of attention recently due to economic concerns and improved in impact resistance as compared to other SAC solder with higher silver content. This work studies the influence of addition of minor zinc (0.1–0.5 wt%) to SAC105 on the interfacial structure between solder and copper substrate during reflow and after aging. Zn has shown significant solubility in Cu–Sn intermetallic compound (IMC) and formed Cu6(Sn,Zn)5 which resided in the bulk microstructure and at the solder/Cu interface. Results reveal that minor Zn addition decreased the thickness of interfacial Cu6Sn5 IMC after reflow and significantly suppressed the growth of interfacial Cu3Sn after thermal aging without changing the IMC’s morphology. It is suggested that Zn exerts its influence by stabilizing Cu6(Sn,Zn)5 and hindering the flow of Sn and Cu atoms at the solder/IMC and IMC/Cu interface. Nanoindentation results showed that Cu6(Sn,Zn)5 exhibited a higher hardness in comparison to Cu6Sn5 and creep performance of SAC + Zn has improved in comparison to that of SAC105.

The size-controllable preparation of chitosan/silver nanoparticle composite microsphere and its antimicrobial performance

The control of chitosan/silver nanoparticle composite microsphere (CAgMs) size is crucial for tuning its function. In the current work, monodisperse organically-modified CAgMs with controllable size were synthesized using a two-step method. The fine-tuning of the microsphere size was confirmed by many reaction parameters while the cross-linking agent was the key research object. Through physical and thermodynamic analysis, we found the cross-linking agent-induced smaller size, higher silver concentration, more heightened glass transition temperature and stronger hydrogen bond network. The as-prepared microspheres exhibited strong bacteriostasis and fresh-keeping function depending on cross-linking agent concentration. The phenomenon is believed to be derived from the difference in microorganism adsorption and killing ability from induced varying specific surface area and encapsulated silver content. Our current work highlights the size-controllable preparation of CAgMs, and based on our findings, small size CAgMs can be a promising candidate in the field of antibacterial and fruit preservation applications.

New Composite Nanomaterials with Antimicrobial and Photocatalytic Properties Based on Silver and Zinc Oxide

Herein we report the synthesis of composites containing nanobio silver, ZnO and phytochemicals in different Ag/Zn molar ratios. First, Ag nanoparticles were prepared using red cabbage extract and then they are covered with zinc oxide obtained also in the same extract by precipitation method. The antimicrobial activity of synthesized nanocomposites was tested against Staphylococcus aureus, Streptococcus, Escherichia coli, Pseudomonas and Candida clinical isolates and compared with that of ZnO functionalized with anthocyanins. The presence of nanobio silver into the nanocomposites enhanced the bactericidal properties demonstrated by slightly larger diameters of growth inhibition zone and lower minimal inhibitory concentrations. S. aureus and Streptococcus strains were more sensitive than the other strains and fungi both for Ag–ZnO nanocomposites and ZnO functionalized with anthocyanins. Also, the presence of silver in the nanocomposites leads to an improved photocatalytic activity (PA) confirmed in the bleaching of Congo red solution. The PA increases with silver content when Ag content is low (up to 1/12 Ag/Zn molar ratio), but decreases significantly for high silver concentration (1/7 Ag/ZnO molar ratio) in the Ag–ZnO nanocomposites.

Adsorption of volatile organic and iodine compounds over silver-exchanged mordenites: A comparative periodic DFT study for several silver loadings

The ability of Ag-exchanged mordenite (Ag-MOR) to capture iodine species such as I2 and CH3I as released for instance during a nuclear accident could be severely limited by the presence of volatile organic compounds (VOCs) that can disrupt their adsorption in the zeolite. Here, using density functional theory (DFT), we investigate in detail the adsorption process of several hydrocarbons (methane, cyclohexane, benzene, and 1,3-dimethylbenzene) and oxygenated compounds (methanol, ethanol, propan-2-ol and propanone) and compare it with the adsorption of I2 and CH3I for different values of the Si/Al ratio of the Ag-exchanged mordenite. It is found that the adsorption process of the iodine species becomes favorable as the Si/Al ratio is decreased. Indeed at high Si/Al ratio, some VOCs such as benzene, 1, 3-dimethylbenzene and propan-2-ol exhibit strong inhibiting effects, while at low Si/Al ratio, only the adsorption of CH3I is limited by the presence of aromatic hydrocarbons. Also, in addition to the elongation of the II bond upon the adsorption of the iodine molecule in Ag-MOR with a high silver content, we found that there is a significant electron transfer between the Ag and I atoms. Thus, our results indicate that the II bond becomes weaker during the adsorption and therefore the formation of AgI precipitates is favored.

Вплив препарату «Шумерське срібло» на життєздатність медоносних бджіл та вміст окремих мікроелементів в їх організмі

Вплив препарату «Шумерське срібло» на життєздатність медоносних бджіл та вміст окремих мікроелементів в їх організмі

The interplay between size and valence state on the antibacterial activity of sub-10 nm silver nanoparticles.

Silver nanoparticles (AgNPs) have attracted enormous interest because of their excellent antibacterial properties, low cytotoxicity and limited evidence for resistance. As a general trend, smaller nanoparticles are considered to have stronger antibacterial activity. In this work we investigate whether this trend is valid for the sub-10 nm region by designing and synthesising three types of sub-10 nm AgNPs (∼1.87, ∼2.93 and ∼6.53 nm) to reveal the influence of size, valence state and structure on the antibacterial potency of AgNPs. We found that NPs with a size of ∼2.93 nm having a high concentration of silver in the first valence state presented the highest bacterial killing potency as well as low cytotoxicity to mammalian cells. The new insights presented in this study open future avenues for the engineering of highly potent silver nanoantibiotics that can be incorporated into future advanced medical devices and therapies capable of protecting patients from infections.

A New Type of Noble Metal Mineralization in Fluidolites of the Poperechny Deposit, Lesser Khingan, Russia

The fluid-explosive breccias of the Poperechny iron–manganese deposit, Lesser Khingan, Russia, contain high concentrations of platinum group elements (PGE), gold, and silver. Noble metals are represented by isoferroplatinum crystals, Os–Ir alloys, PGE sulfoarsenides, and gold grains with a size of tenths of a millimeter and micron-sized segregations of native silver. The mineral composition of the PGE of the Poperechny deposit is consistent with that of the ore and placer objects of the Ural–Alaskan type and corresponds to the isoferroplatinum–osmium magmatic assemblage. The euhedral morphology of the isoferroplatinum and PGE sulfoarsenides indicates that they were formed in a stable environment at the crust–mantle boundary owing to partial melting of slab rocks. The appearance of PGE minerals in the magmatic–hydrothermal system under subsurface conditions is related to a highly mobile gas-saturated fluid flux capable of transferring deep mineral phases. The high content of PGE (up to 11.3 g/t), gold (up to 2.58 g/t), and silver (up to 256 g/t) in the fluidolites of the Poperechny deposit makes it possible to revise the criteria for searching for the bedrocks and placer sources of noble metals in the Lesser Khingan.

Determination of silver concentration in tomato seeds (Solanum Lycopersicum L.) exposed to silver nanoparticles using AAS-F and a validated method

The interaction of silver nanoparticles with Tomato seeds (Solanum Lycopersicum L.) was studied; the amount of silver uptake by tomato seeds was quantified by using flame atomic absorption. The absorption analysis was carried out according to the performance study of the method to estimate the detection and quantification limits as well as the accuracy. The seeds were exposed at different silver concentrations and different times. A simple method has been developed for the determination of silver content in aqueous matrices by acid digestion followed by atomic absorption spectroscopy flame; it was found that the acid digestion is efficient for extraction of the analyte in a single step. The limits of quantification achieved in the analytical method allow the determination of silver on plant tissue, the highest silver uptake in the tomato seeds was obtained with the treatment using the highest silver concentration (10 mM) and longer exposition time (48 h).

Effect of catalyst preparation for the simultaneous removal of soot and NOx

La0.7Ag0.3MnO3 perovskite-like catalyst was prepared using three synthetic routes, microwaved-assisted (MW) microwaved-assisted hydrothermal (HMW) and solid state (SS) with the aim of studying catalyst preparation method effect on the simultaneous removal of soot and NOx under loose contact condition. The materials were characterized using various analytical techniques, such as XRD, XPS, H2-TPR and O2-TPD. Among the prepared solids, the MW catalyst showed the best catalytic performance for the simultaneous removal since it was the one with the lowest soot ignition temperature (160 °C), the lowest temperature for the maximum NOx reduction (328 °C), the highest NOx reduction efficiency (60%); and an intermediate T50 (371 °C) for soot oxidation. Results further showed that a rapid synthesis using short microwave irradiation time (6 min) for the precursor solution and short calcination times for the final solid (1 h) produced smaller particles (13 nm) with a high silver (Ag+) content incorporated into perovskite lattice structure thus facilitating the formation of oxygen vacancies as active sites. In fact, the increment in the oxygen vacancies correlated with the increment of surface oxygen content (α-oxygen) that along with the segregated metallic silver amount allowed inferring that both active sites are needed for the simultaneous NO and soot removal. Finally, based on our results it was suggested that both NO and O2 are adsorbed from the gaseous phase on the active sites (oxygen vacancies and Ago) of the catalyst surface to form NO2 as an intermediate that quickly reacts with soot to yield CO2 and N2.

A Microstructural and Wear Resistance Study of Stainless Steel-Ag Coatings Produced through Magnetron Sputtering

This paper presents a study of the tribological properties of stainless steel coatings with varying Ag contents, deposited via magnetron sputtering. The growth of the coatings was done in Ar and Ar + N2 atmospheres in order to change the crystalline phase in the coating. The analysis of the chemical composition was performed using energy-dispersive X-ray spectroscopy (EDS) and the structural analysis was performed via X-ray diffraction (XRD). The adhesive wear resistance and the friction coefficient were evaluated using the ball-on-disk test with a ball of alumina. The coatings’ adhesion was measured with a scratch tester and the mechanical properties were evaluated with a nanoindenter. The morphology of the films and the wear track were characterized via scanning electron microscopy (SEM). By means of XRD, phases corresponding to the body-centred cubic (BCC) structure were found for the coatings deposited in an inert atmosphere and face-centred cubic (FCC) for those deposited in a reactive atmosphere. A more compact morphology was observed in coatings with a higher silver content. The values of the hardness increased with an increase in the silver content and the presence of nitrogen in the coatings. In the wear traces, mainly mechanisms of oxidative and adhesive wear and plastic deformation were found. The coefficient of friction decreased with an increase of silver in the coatings, whereas the wear rate decreased.

Effect of cluster interface structure on the spontaneous escape behavior of silver in ion plating coatings and its inhibition mechanism

In order to study the spontaneous escape behavior of silver in ion plating coatings and its inhibition mechanism, a series of silver-doped titanium nitride coatings were prepared by magnetron sputtering. The effect of cluster interface structure on the spontaneous escape behavior of silver in ion plating coatings were observed, and various thicknesses of homogenous silver-free barrier layers were explored to achieve the permanent retention of silver. Results showed that for silver-doped titanium nitride coatings prepared with the silver target current increased from 0.01 A to 0.2 A, more spontaneously escaped silver particles were observed at the cluster interface of the coating and were far from being crystallized into a layered structure. Approximately 500 nm pure titanium nitride surface cover could achieve the permanent retention of silver in titanium nitride coatings with a high dopant content of silver. The cluster interfaces of the titanium nitride coating interdigitated with each other to form a dendritic network structure. The interdigitated dendritic network structure blocked the spontaneous escape of silver and achieved the permanent retention of silver in the titanium nitride coating.

Silver addition to a cobalt Fischer–Tropsch catalyst

Silver is known to promote F–T catalysts as a reduction promoter, although it has also been observed to affect catalytic performance of, for instance, cobalt nanoparticles. In this work, a series of silica-supported cobalt catalysts with a constant platinum content (0.04 wt%) and varying silver content were characterized and tested. Characterization shows that mainly coordinatively unsaturated cobalt atoms are substituted at low silver content (probed by N2 IR). Adding more silver results in replacement of both coordinatively unsaturated sites and planar sites (probed by H2-chemisorption and TEM-EDS). The presence of silver on the cobalt surface affects both structure-sensitive CO dissociation and structure-insensitive hydrogenation reactions. The Boudouard reaction shows that the CO dissociation rate decreases with increasing silver content. Hampered CO dissociation is also apparent from temperature-programmed CO IR spectroscopy. However, even at high silver content the surface still contains step-edge sites that can dissociate CO and a small amount of carbon is deposited (quantified by TPH). During the CO hydrogenation at 260 °C, CO conversion is reduced by less than 30% when 8.8 wt% silver is added. This does not correlate well with the loss in cobalt surface area measured by chemisorption (decreases by 93%) or CO dissociation rate probed by CO disproportionation (decreases by 90%). This mismatch is mainly because that the CO consumption rate under methanation condition is largely controlled by carbon and oxygen hydrogenation, rather than CO dissociation. On the other hand, transient experiments show that silver accelerates oxygen-removal steps. It turns out that CO conversion is only moderately affected by silver. The coverage of hydrogenation sites – mostly terrace sites – by silver causes slower CH4 formation. Longer residence of CHx intermediates (determined by SSITKA) accordingly leads to an increase in chain-growth probability and therefore higher C2+ selectivity. SSITKA also confirms that the decrease in steady-state CO/CHx coverage qualitatively correlates to the loss in cobalt surface area. Another consequence of slower hydrogenation is that the olefins-to-paraffins ratios are higher when silver is added to the catalyst. Importantly, covering the cobalt surface with silver affects the F–T product distribution in a similar manner as graphitic carbon deposited on terrace sites as we reported earlier.

Dosing, Not the Dose: Comparing Chronic and Pulsed Silver Nanoparticle Exposures.

The environmental impacts of manufactured nanoparticles are often studied using high-concentration pulse-additions of freshly synthesized nanoparticles, while predicted releases are characterized by chronic low-concentration additions of weathered particles. To test the effects in wetlands of addition rate and nanoparticle speciation on water column silverconcentrations,ecosystem impacts, andsilveraccumulation by biota,we conducted a year-long mesocosm experiment. We compared a pulse addition of Ag0-NPs to chronic weekly additions of either Ag0-NPs or sulfidized silver nanoparticles. The initially high water column silver concentrations in the pulse treatment declined such that after 4 weeks it was lower on average than in the two chronic treatments. While the pulse caused a marked increase in dissolved methane in the first week of the experiment, the chronic treatments had smaller increases in methane concentration that were more prolonged between weeks 28-45. Much like water column silver, most organisms in chronic treatments had comparable silver concentrations to the pulse treatment after only 4 weeks, and all but one organism had similar or higher concentrations than the pulse treatment after one year. Pulse exposures thus both overestimate the intensity of short-term exposures and effects and underestimate the more realistic long-term exposure, ecosystem effects, and accumulation seen in chronic exposures.

Electron-beam modification of optical properties of phosphate glasses with high concentration of silver

The results of experimental study of silver-containing lanthanum-phosphate glasses, modified by electron irradiation with electrons energy E = 5 and 50 keV and thermal treatment are presented. The concentration of Ag2O in glasses was 17 and 30 mol%. It is shown that initially silver is contained in glasses mainly in a state of subnanosized neutral molecular clusters (MCs). Local electron irradiation results in the increase of MCs concentration in the irradiated zone. This process is accompanied by the appearance of luminescence outside the irradiated zone. Redistribution of silver during electron irradiation is confirmed by X-ray spectral microanalyses. During irradiation with E = 5 keV some part of silver migrates to the glass surface, forming the solid silver film. During thermal treatment the growth of silver MCs takes place, and, at last, they form silver nanoparticles (NPs).

Integration of Functional Nanomaterials in Biopolymer Composites Using Ionic Liquid Based Methods

In this work, metallic silver nanoparticles were synthesized in linen powders by the process of incipient wetness impregnation. Linen powders with varying concentrations of silver particles were prepared by control of the amount of silver nitrate added during the synthesis. These composite materials were characterized by XPS, SEM, EDS, ATR-IR, and Raman. XPS showed that the silver was predominately zero valent. SEM did not show any distinct silver particles at the limit of the instrument resolution. However, EDX indicated a uniform distribution of silver in all linen powders. The ATR-IR exhibited no significant change in the linen substrate after silver nanoparticle synthesis. Raman spectroscopy of the linen powders displayed significant variability depending upon the amount of silver present. At low silver concentrations, the auto fluorescence of the lignin in the Linen powders dominated the Raman spectrum. At higher silver concentrations, the auto fluorescence declined dramatically and the Raman spectra of the cellulose emerged. At 10 wt % silver, the fluorescence was completely quenched and the cellulose spectrum was significantly enhanced. These results are consistent with the presence of nanoparticles that quench underlying linen fluorescence and give a surface enhanced Raman spectrum of the linen. The linen containing silver nanoparticles were then added to an IL to make an “ink” that was used to print patterns on a cellulose substrate.

FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes

A set of ancient Antoninianus silver coins, dating back between 249 and 274 A.D. and minted in Rome, Galliae, Orient and Ticinum, have been characterized. We use, for the first time, a combination of nano-invasive (focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), voltammetry of microparticles (VIMP)) and destructive techniques (scanning electron microscopy (SEM-EDX) and electron microprobe analysis (EMPA)) along with non-invasive, i.e., micro-Raman spectroscopy. The results revealed that, contrary to the extended belief, a complex Ag-Cu-Pb-Sn alloy was used. The use of alloys was common in the flourishing years of the Roman Empire. In the prosperous periods, Romans produced Ag-Cu alloys with relatively high silver content for the manufacture of both the external layers and inner nucleus of coins. This study also revealed that, although surface silvering processes were applied in different periods of crisis under the reign of Antoninii, even during crisis, Romans produced Antoninianus of high quality. Moreover, a first attempt to improve the silvering procedure using Hg-Ag amalgam has been identified.

Effect of Ag Content and β-PbO2 Plating on the Properties of Al/Pb-Ag Alloy

Due to the excellent electrical conductivity and mechanical properties, Al/Pb-Ag alloy has a great potential to be used as an alternative anode for zinc electrowinning. In this work, the effects of Ag content and surface plating with β-PbO2 on the anodic behavior and reaction kinetics were investigated by cyclic voltammetry (CV), anodic polarization curves, electrochemical impedance spectroscopy (EIS) and corrosion rate test. The phase composition and microscopic morphology of the anode oxide layers after electrolysis were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results indicate that high content of silver and electroplating β-PbO2 layer can increase the oxygen evolution activity, electrocatalytic activity and corrosion resistance of the anodes. Al/Pb-0.75%Ag plating β-PbO2 has the lowest oxygen evolution overpotential followed by Al/Pb-0.3%Ag plating β-PbO2, Al/Pb-0.75%Ag and Al/Pb-0.3%Ag. Besides, high content of silver is more beneficial to improving corrosion resistance compared with electroplating β-PbO2 on anode. In addition, the phase composition of four anodes layer are mainly composed of α-PbO2, β-PbO2, Pb and PbO.