Low Silver Content Research Articles

Electrospun poly(N-vinylpyrrolidone) membranes with Ag nanoparticles for wound dressings: Production and characterization

Wound dressings have long been used to promote the healing of skin injuries. In the work reported here, fibrous membranes were produced by electrospinning poly(N-vinylpyrrolidone) (PVP) solutions containing silver nitrate at varying mass ratios (1:200, 1:100 and 1:50 AgNO3:PVP). PVP solutions without AgNO3 were used as a control. The electrospun membranes were irradiated using 254 nm UV light to simultaneously photo-crosslink PVP and promote the formation of silver nanoparticles (AgNPs). The formation of AgNPs was confirmed by scanning electron microscopy and transmission electron microscopy, as well as by detecting the surface plasmon resonance peak at 420 nm in the UV–Vis spectrum during release studies. The swelling rate of fibrous membranes was lower for those containing AgNPs compared to PVP-only membranes. The Kirby-Bauer diffusion test performed against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans showed that all AgNPs-containing membranes exhibited an inhibitory effect on all microorganisms tested. The in vitro cytotoxicity assay showed that membranes with lower silver concentration were less cytotoxic. This study presents a simple route to producing a wound dressing with antimicrobial action that has a swelling behavior capable of absorbing exudates, provides controlled release of silver and has low cytotoxicity.

A simple optical sensor for the simultaneous determination of trace amounts of silver and gold nanoparticles in water by cloud point microextraction

Nowadays, metal nanoparticles are widely used in many fields due to their excellent properties. This has led to an increasing presence of these species in water, which, although in very low concentrations, can cause damage to ecosystems. These nanomaterials are currently considered as emerging pollutants in water, so there is a need to know their concentrations. In particular, gold and silver nanoparticles are among the most widely used. Therefore, the development of simple methods that allow their determination even at trace concentrations is of interest. In this work, a method has been developed for the simultaneous determination of low concentrations of silver and gold nanoparticles (AgNPs and AuNPs, respectively) in water by cloud point microextraction using Triton X-114 as extractant and UV–Vis molecular spectrophotometry. It is a simple, environmentally friendly method with an easy-to-use portable instrument that requires only a microdrop of the extracted phase for the analysis of both species. Detection limits reached were 17 and 15 µg L−1 for AgNPs and AuNPs, respectively. The enrichment factors were 160 for AgNPs and 165 for AuNPs.

Direct electron beam writing of silver using a β-diketonate precursor: first insights.

Direct electron beam writing is a powerful tool for fabricating complex nanostructures in a single step. The electron beam locally cleaves the molecules of an adsorbed gaseous precursor to form a deposit, similar to 3D printing but without the need for a resist or development step. Here, we employ for the first time a silver β-diketonate precursor for focused electron beam-induced deposition (FEBID). The used compound (hfac)AgPMe3 operates at an evaporation temperature of 70-80 °C and is compatible with commercially available gas injection systems used in any standard scanning electron microscope. Growth of smooth 3D geometries could be demonstrated for tightly focused electron beams, albeit with low silver content in the deposit volume. The electron beam-induced deposition proved sensitive to the irradiation conditions, leading to varying compositions of the deposit and internal inhomogeneities such as the formation of a layered structure consisting of a pure silver layer at the interface to the substrate covered by a deposit layer with low silver content. Imaging after the deposition process revealed morphological changes such as the growth of silver particles on the surface. While these effects complicate the application for 3D printing, the unique deposit structure with a thin, compact silver film beneath the deposit body is interesting from a fundamental point of view and may offer additional opportunities for applications.

Silver recovery into lead bullion from a lead concentrate by direct reduction with Na2CO3 and SiC reagents

ABSTRACT Silver has been recovered in lead bullion from a lead concentrate throughout a direct reduction process. The lead concentrate was obtained from a plant that processes polymetallic minerals located in the central mining area of Mexico. The direct reduction process has been tested through mixtures of Na2CO3 and SiC that were put in contact with the lead concentrate at 1000 °C for 60 min to produce lead bullion containing silver and slag. The produced lead bullion containing silver and the slag after direct reduction trials showed that it is possible to recover about 90% of lead and 86.5% of silver into the lead bullion, leading to a low silver content in the slag phase (<0.2 wt.%). The slag was constituted mainly by sodium silicate compounds such as Na2SiO3, Na4SiO4, and Na2Si2O5, when 50 wt. % of Na2CO3 and 10 wt. % of SiC regarding the initial charge of the lead concentrate was used. The proposed process has been assisted thermodynamically by the software FactSage 7.6, which allowed us to predict the main expected compounds and understand the process mechanism for silver recovery into a lead bullion using Na2CO3 and SiC reagents.

Polymer-Based Hydroxyapatite-Silver Composite Resin with Enhanced Antibacterial Activity for Dental Applications.

The primary objective of this investigation was to synthesize a resin incorporating nanoparticles of hydroxyapatite and silver (HA-NpsAg) to enhance biocompatibility and antimicrobial efficacy, thereby facilitating potential implementation within the dental industry. These enhancements aim to ensure reliable, durable, functional, and aesthetically pleasing restorations while concurrently reducing susceptibility to bacterial colonization within the oral cavity. Hydroxyapatite powders were prepared using the sol-gel method and doped with silver nanoparticles obtained by chemical reduction. The crystalline amorphous calcium phosphate powder had a particle size of 279 nm, and the silver nanoparticles had an average diameter of 26.5 nm. Resin spheres containing HA-NpsAg (RHN) were then synthesized at two concentrations (0.5% and 1%) by dissolving the initial monomer mixture in tetrahydrofuran. Subsequent antimicrobial evaluations were conducted via agar diffusion and turbidimetry, employing three strains of Gram-negative bacteria (E. coli, K. oxytoca, and P. aeruginosa) and three strains of Gram-positive bacteria (S. mutans, S. aureus, and B. subtilis). The findings revealed that P. aeruginosa exhibited maximum susceptibility to RHN powder at a concentration of 0.5%, while RHN powder at 1% concentration demonstrated maximal inhibition against S. aureus and S. mutans. Overall, our study highlights the successful synthesis of a dental resin with hydroxyapatite and silver nanoparticles, exhibiting bactericidal properties at low silver concentrations. These findings hold promise for enhancing dental materials with improved antimicrobial efficacy and clinical performance.

Uniformly coated Cu@Ag core-shell particles with low silver content: Hydroxy acid as a complexing agent with “double-sided adhesive” function

The Cu@Ag core-shell particles are the highly anticipated functional materials in electronic applications which are required to be high electrical conductivity, good thermal properties and low cost. However, it remains a challenge to obtain a completely and uniformly coated Ag shell in low silver content. During the coating process, it is essential to regulate the reduction of Ag+ on the surface of Cu to ensure uniformly silver shell. We developed a strategy to prepare uniformly coated Cu@Ag particles by employing hydroxy acids as complexing agents with “double-sided adhesive” function. Compared to conventional complexing agents, the employed hydroxy acids can not only coordinate with Ag+ but also complex with Cu due to the more carboxyl and hydroxyl groups which act like a “double-sided adhesive”, that can pull Ag+ to the surface of Cu, and then accomplish the coating of Ag with replacement and reduction reaction. The impact of different types of hydroxy acids as complexing agents on the coating effect of silver-clad copper powder was investigated when the silver addition was 15 %. Results indicated that the obtained Cu@Ag particles with tannic acid as complexing agent show high coating quality layer with low surface sliver content (11.4 %). Moreover, the obtained Cu@Ag particles exhibit good dispersibility, promising thermal stability and low electrical resistivity (30 μΩ·cm).

A modern polymer based wound care coating for wound management

Pain management at phase 1 of the wound process includes wound cleaning due to the lysis of purulent-necrotic masses, control of the pathogenic microflora, and evacuation of wound discharge. These factors are achievable with a new composite depo-material having the textile base, hydrogel composition based on biopolysaccharide sodium alginate with immobilized active components – proteolytic enzyme of plant origin- papain and antimicrobial salt-like silver. Biosynthesis of silver nanoparticles and its presence in the composition in the cation form increases efficacy and eliminates toxicity of the treatment due to low silver concentration.

Biological properties of a novel solution based on silver nanoclusters for arresting dentin caries.

To test the biological properties of a novel non-restorative treatment method for arresting dentin caries based on silver nanoclusters (AgNCls) synthesized in polymethacrylic acid (PMAA). Synthesis of AgNCls was performed by photoreduction of AgNO3 in PMAA with 355 nm/wavelength light. AgNCls/PMAA was characterized by absorption/fluorescence spectroscopy and optical and atomic force microscopy. The stability of the clusters in an aerated PMAA solution was evaluated by means of fluorescence spectroscopy. Cytotoxicity was assessed using the MTT assay and antibacterial effect was determined for minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and colony forming (CFU) of Streptococcus mutans (S. mutans) and Lactobacillus acidophilus (L. acidophilus). 38% Silver Diammine Fluoride (SDF) was used for the control groups. Chemical and structural identity of the clusters did not change within 9 months; Cell viability of 92%-89% was found after 24-48 h respectively. MIC and MBC were determined from 1:16 and 1:8 dilutions, respectively. Log CFU counts of S. mutans, and L. acidophilus treated with AgNCls/PMAA (3.4 ppm of silver) were significantly lower than in the control groups and even lower than when the same bacterial strains were treated with SDF (15,525 ppm of silver). AgNCls/PMAA presented chemical stability, acceptable cytotoxicity, and a potential antibacterial effect for strains associated with caries lesions at very low concentrations of silver.

Ampacet launches ProVital™+ GermsClean, medical-grade antimicrobial masterbatch

Ampacet ProVital+ Germsclean is an additive developed to protect plastic components in healthcare facilities from the proliferation of microorganisms. It is claimed to offer excellent performance and protection from a wide spectrum of pathogens, with a lower addition rate than traditional competitive solutions and with a very low silver content, limiting discoloration.

Silver Nanoparticle-PEDOT:PSS Composites as Water-Processable Anodes: Correlation between the Synthetic Parameters and the Optical/Morphological Properties.

The morphological, spectroscopic and rheological properties of silver nanoparticles (AgNPs) synthesized in situ within commercial PEDOT:PSS formulations, labeled PP@NPs, were systematically investigated by varying different synthetic parameters (NaBH4/AgNO3 molar ratio, PEDOT:PSS formulation and silver and PEDOT:PSS concentration in the reaction medium), revealing that only the reagent ratio affected the properties of the resulting nanoparticles. Combining the results obtained from the field-emission scanning electron microscopy analysis and UV-Vis characterization, it could be assumed that PP@NPs' stabilization occurs by means of PSS chains, preferably outside of the PEDOT:PSS domains with low silver content. Conversely, with high silver content, the particles also formed in PEDOT-rich domains with the consequent perturbation of the polaron absorption features of the conjugated polymer. Atomic force microscopy was used to characterize the films deposited on glass from the particle-containing PEDOT:PSS suspensions. The film with an optimized morphology, obtained from the suspension sample characterized by the lowest silver and NaBH4 content, was used to fabricate a very initial prototype of a water-processable anode in a solar cell prepared with an active layer constituted by the benchmark blend poly(3-hexylthiophene) and [6,6]-Phenyl C61 butyric acid methyl ester (PC60BM) and a low-temperature, not-evaporated cathode (Field's metal).

Activation analysis of the lead coolant in SUNRISE-LFR

A lumped, zero-dimensional, mass transport model is combined with a depletion matrix solver to study the influence of coolant circulation on radionuclide build-up in a small lead-cooled fast reactor. It is shown that the addition of coolant circulation results in a lower activity for a minority of studied nuclides, and it is thus recommended to consider stagnant coolant when licensing a reactor. Activation analysis of three different lead qualities potentially used in SUNRISE-LFR is performed, and the result shows that a low silver content is desirable to simplify maintenance and decommissioning.

Tools and jewels: An analytical study of copper-alloy artefacts from Early Bronze Age Thasos, north Aegean

Thasos is an island in the north Aegean with a long tradition in mining and metallurgical production the emergence of which could be traced to the end of the Neolithic and the beginning of the Early Bronze Age (c. 3200 BCE). The current study is focused on copper alloy artefacts that were found in several Early Bronze Age settlements on the island to provide an understanding of how they were produced and utilised/consumed by their users. Application of laboratory instrumental techniques, namely compositional analysis by X-ray Fluorescence and metallography coupled by Scanning Electron Microscopy (SEM/EDS) are used to illuminate our understanding of the methods utilised for their fabrication and the choice of certain alloys that were common during the Early Bronze Age. Results have revealed the predominance of arsenical copper fabricated by casting, followed by stages of hammering and annealing. A single example of a leaded copper object shows no parallels among the studied assemblage or other contemporary finds. The average arsenic contents of 2.9 wt% might be the result of accidental alloying of copper with arsenic-bearing copper minerals or indeed a conscious selection of mixed ores that contained both metals. Geological information is taken into consideration attempting to locate the possible sources of copper and arsenic-bearing minerals on the island that were potentially utilised as raw materials. Results point to the possible utilisation of fahlores (tennantite in particular) from a mining location close to Limenaria that could yield arsenical copper in a single stage smelting process. Considering the co-occurrence of arsenic and low silver contents in the fahlores from this location, they match well to the minute silver contents detected in two artefacts of the assemblage under study. Such preliminary findings are of special importance as they contribute to the ongoing discussion concerning the production of arsenical copper across the Aegean during the EBA.

Microstructure and morphology of the soldering interface of Sn–2.0Ag–1.5Zn low Ag content lead-free solder ball and different substrates

Eutectic Sn–Ag–Cu lead-free solder has limited applications due to cost and reliability issues. Sn–Ag–Zn solder has the advantages of low melting point, good mechanical properties and reliable welding interface. However, the research system of low silver content Sn–Ag–Zn solder is incomplete. In this paper, Sn–2.0Ag–1.5Zn low silver content alloy solder is soldered to different substrates. The interfacial reaction after soldering and the microstructure and reliability under different aging treatment conditions are studied. Sn–2.0Ag–1.5Zn solder is made into solder balls by direct melting method. The solder balls are placed in a solder strength tester to be heated and welded to the substrate, and then the solder joints are placed in a heating furnace for aging treatment. The results show that the solder is soldered to the bare Cu substrate, and a dense double-layer Intermetallic Compound (IMC) structure of Cu5Zn8 and Ag3Sn is formed at the interface after aging treatment. The double-layer structure blocks each other, limiting the development of copper-tin IMCs. The solder is soldered with the Cu substrate electroplated with Ni barrier layer, and the soldering interface forms a thin layer of Ni3Sn4 metal compound. After aging for 1000 h, the thickness of Ni3Sn4 is about 1 μm, the thickness of Ni barrier layer is kept at 2–3 μm, and the barrier effect of Ni barrier layer is stable. Sn–2.0Ag–1.5Zn solder has excellent loss performance in long aging treatment. It has good heat-resistance aging treatment, good quality of solder connection, high interface reliability and less environmental pollution. The low silver content in Sn–2.0Ag–1.5Zn solder results in a significant cost reduction. Coarse IMC Ag3Sn is not easily formed. The optimized ratio of Ag and Zn in Sn–2.0Ag–1.5Zn solder improves the strength and toughness of the solder joint. The performance has been improved, and it is a very promising alloy solder.

Composition-dependent chemical ordering predicted in Pt-Ag nanoalloys.

Pt-Ag nanoalloys display an astonishing chemical organization depending on their size and composition. Reversed size-dependent stabilization of ordered nanophases [J. Pirart et al., Nat. Commun., 2019, 10, 1982-1989] has recently been shown around equiconcentration. We extend this study by a theoretical investigation on the whole range of compositions showing a significant composition-dependent chemical ordering in Pt-Ag nanoalloys. At a low silver content, the surface exhibits a strong Ag segregation coupled to a (2 × 1) superstructure on the (100) facets. By increasing the silver concentration, the system displays an L11 ordered phase in the core, interrupted in a narrow range of concentrations by a concentric multishell structure characterized by an alternation of Ag-pure/Pt-pure concentric layers starting from the surface shell to the core. Although the L11 ordered phase has been observed experimentally, the concentric multishell structure is lacking due to the difficulty of the experimental characterization.

Mordenite-Supported Ag+-Cu2+-Zn2+ Trimetallic System: A Variety of Nanospecies Obtained via Thermal Reduction in Hydrogen Followed by Cooling in an Air or Hydrogen Atmosphere.

Multimetallic systems, instead of monometallic systems, have been used to develop materials with diverse supported species to improve their catalytic, antimicrobial activity, etc., properties. The changes in the types of nanospecies obtained through the thermal reduction of ternary Ag+-Cu2+-Zn2+/mordenite systems in hydrogen, followed by their cooling in an air or hydrogen atmosphere, were studied. Such combinations of trimetallic systems with different metal content, variable ratios (between them), and alternating atmosphere types (during the cooling after reducing the samples in hydrogen at 350 °C) lead to diversity in the obtained copper and silver nanospecies. No reduction of Zn2+ was evidenced. A low silver content leads to the formation of reduced silver clusters, while the formation of nanoparticles of a bigger size takes place in the trimetallic samples with high silver content. The cooling of the reduced trimetallic samples in the air causes the oxidation of the obtained metallic clusters and silver and copper nanoparticles. In the case of copper, such conditions lead to the formation of mainly copper (II) oxide, while the silver nanospecies are converted mainly into clusters and nanoparticles. The zinc cations provoked changes in the mordenite matrix, which was associated with the formation of point oxygen defects in the mordenite structure and the formation of surface zinc oxide sub-nanoparticles in the samples cooled in the air.

Electron Beam Brazing of Titanium and Stainless Steel Dissimilar Joints with Ag-Based Filler

In this work, electron beam was used for butt brazing of austenitic stainless steel with grade 2 titanium. Due to its low solidus temperature and high silver content, AWS BAg-21 filler containing Ag, Cu, Sn and Ni was selected. The joints were brazed with a defocused oscillating beam using offset. The resulting brazed joints were subjected to static tensile testing, light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) analysis and hardness tests. By using appropriate parameters it was possible to reduce the phenomenon of diffusion of titanium atoms into the joint, which improved the properties of the obtained joints. The maximum tensile strength obtained was 244.2 MPa.

Impact of silver nanoparticle concentration in alginate microcapsules on their effects on morphological changes in periodontitis

Objective: to evaluate the effects of alginate microcapsules on morphological changes in periodontitis depending on silver nanoparticle concentration in them. Materials and Methods. The study was conducted on 30 rats distributed among three groups of 10 animals: the comparison group comprising animals with an experimental model of periodontitis and two experimental groups including animals with 5-week periodontitis, which were subjected to applications of the gel containing microcapsules with high (0.25 M, Group 1) and low (0.1 M, Group 2) concentrations of silver on the surface of their gums. To assess morphological changes, the mandible was sampled for subsequent examination. Results. In animals with periodontitis, changes in the supporting structure of the tooth took place, including defibration and perivascular edema in periodontal ligament of the tooth, and bone resorption via its replacement with connective tissue. The application of a gel containing microcapsules with silver nanoparticles led to a partial reduction of such disorders: particularly, it reduced bone resorption and its replacement with connective tissue. Destructive changes in periodontal tissues caused by gel with a high content of silver nanoparticles (0.25 M) were less pronounced than those caused by capsules with a low content of silver (0.1 M). Conclusion. Gels containing microcapsules with silver nanoparticles contributed to the reduction of destructive changes in the supporting structure of the tooth in periodontitis. The severity of the effects of the gel increased with an increase in the content of silver nanoparticles in alginate microcapsules.

How small changes make a difference: Influence of low silver contents on the effect of RbF‐PDT in CIGS solar cells

AbstractDespite the efficiencies above 20% achieved with (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells, further efficiency improvements are necessary. One possibility is the implementation of a postdeposition treatment (PDT) process. The aim of this study is therefore to investigate the effect of rubidium‐fluoride (RbF)‐PDT on the performance and physical properties of the ACIGS absorber. For this purpose, the RbF source temperature of the PDT process of ACIGS films with Ag/(Ag+Cu) (AAC) ratios of 5% from a multistage co‐evaporation inline process was systematically varied. It was shown that the efficiency of the devices is reduced by the PDT process, unlike observed for Cu(In,Ga)Se2 (CIGS) absorber, and is strongly influenced by the amount of rubidium. The behavior can be attributed to a strong reduction of the doping, which results from a changed doping mechanism. Furthermore, evidence for the formation of an additional layer was found. In addition, deep level transient spectroscopy (DLTS) measurements were performed on the samples showing a strong signal at low temperatures. This minority trap signal is strongly influenced by the amount of Rb and shows a systematically changing energetic position towards the middle of the band gap and an increasing density. Based on pulse variation measurements, the associated defect could be identified as an extended defect, indicating a location of the defect at grain boundaries.

Novel epoxy adhesives based on conductive micron‐sized silver flowers

AbstractLow silver contents are desirable for electrically conductive adhesives (ECAs) due to the high cost of silver. In the present work, micro‐sized flower‐like silver particles (MFSPs) with long and thin petals are prepared by a novel, green, and facile chemical reduction method in an aqueous solution. The effects of reactant mass ratio and reactant concentration are investigated to control the morphology and size of MFSPs. Three kinds of MFSPs with different sizes are filled into an epoxy resin to prepare novel ECA. Due to the easily formed conductive paths by such morphological silver particles, the as‐prepared MFSP/epoxy composite adhesive has a low percolation threshold, a high conductivity, and high adhesion strength at a very low silver content. When considering the optimal combination of low electrical resistance and high adhesion strength, the MFSP obtained at the 1.5:1 ratio of ascorbic acid to silver nitrate is promising for preparing the ECA with a low Ag content of 30 wt% which is the lowest content for ECAs compared with the literature. The synthesis process of MFSPs has the advantages of mild condition, simple process, and environmental friendship. This study provides a new way to prepare highly conductive Ag/epoxy adhesives with low silver contents.

Biobased Chicken Eggshell Powder for Efficient Delivery of Low-Dose Silver Nanoparticles (AgNPs) to Enhance Their Antimicrobial Activities against Foodborne Pathogens and Biofilms.

Despite the current sanitation practices to decontaminate food-contact surfaces, persistent biofilms still pose significant threats to human health by inducing cross-contamination. This study aims to enhance the antimicrobial activity of low-dose silver nanoparticles (AgNPs) against foodborne pathogens and their biofilms through the development of a biobased delivery carrier for metallic nanoparticles. In this study, chicken eggshell powder (EP) was used as a biocompatible delivery carrier, and it possesses a strong ability to encapsulate green-synthesized AgNPs with an encapsulation efficiency of 80.18%. The EP carriers stabilized AgNPs in an organic-rich environment and prevented the aggregation of nanoparticles. The results of antimicrobial test demonstrate that EP significantly enhanced the antimicrobial efficacy of low-dose AgNPs (2 μg/mL), enabling 5-log reductions of planktonic Escherichia coli and Listeria innocua within 25 min and 60 min treatments, respectively, even in the presence of high organic content (chemical oxygen demand, COD = 1000 mg/L). Due to the high affinity of EP to bind biofilms, the encapsulated low-dose AgNPs can inactivate approximately 2-log CFU/cm2 of biofilms within a 2-h treatment. The proposed AgNPs@EP composite with a low silver concentration (2 μg/mL) can effectively inactivate and remove biofilms from food-contact surfaces in which such a low concentration of AgNPs is unlikely to induce negative impacts on human health and environment. Therefore, this antimicrobial AgNPs@EP composite can potentially be used as a biobased sanitizer for food-contact surfaces in a food manufacturing plant.