Silver Ag Research Articles

Bipolar resistive switching studies in amorphous barium titanate thin films in Ag/am-BTO/ITO capacitor structures

The electroforming free bipolar resistive switching characteristics of amorphous barium titanate (am-BTO) thin films in Ag/am-BTO/ITO capacitor structures were systematically evaluated. The dot point capacitor structures were fabricated by using RF-DC sputtering deposition on ITO coated commercial glass substrates. Varied thicknesses of 142, 100, and 70 nm am-BTO thin films were utilized as a switching medium for exploring the resistive switching phenomena. The amorphous nature and topographical surface were probed with X-ray diffraction and atomic force microscopy techniques. The on/off resistance ratios, SET, RESET voltages, retention, and endurance parameters extracted from current-voltage (I-V) measurements demonstrate stable resistive switching. Space charge limited current conduction and ohmic conduction phenomena were found to be dominant in high resistance and low states of the junctions. The rupture formation upon the Ag active electrode and reduction in capacitance after the application of voltage specify the silver Ag+ ion mediated filament conduction mechanism for the observed bipolar switching phenomena.

Synthesis, Characterization, and Antimicrobial Properties of Sparfloxacin-Mediated Noble Metal Nanoparticles

The aim of the current research finding was to synthesize, characterize and antibacterial evaluation of sparfloxacin-mediated noble metal nanoparticles. Noble metal [silver (Ag), and gold (Au)] nanoparticles (NPs), mediated with fluoroquinolone, an anti-bacterial drug [Sparfloxacin, (Sp)], was synthesized by a facile and convenient procedure. Formulated Ag-Sp NPs, and Au-Sp NPs exhibited stability against variation in pH, NaCl solution, temperature, and time. The structural topographies of Ag-Sp, and Au-Sp NPs were determined by fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM) atomic force microscopy (AFM), and energy dispersive X-ray (EDX). UV-Vis revealed the formulation of NPs by showing typical surface Plasmon absorption maxima at 410 nm for Ag-Sp NPs and 555 nm for Au-Sp NPs. The AFM and SEM analysis ascertained stable mono dispersed Ag-Sp NPs and Au-Sp NPs in the size range of 40-50 nm, and 70-80 nm, respectively. Ag-Sp, and Au-Sp NPs exhibited antibacterial traits against Bacillus subtilis, Staphylococcus aureus, and Klebsiella pneumonia, showing a zone of inhibition (ZOI) ranging from 20±0.98 mm to 24±0.94 mm (Ag-Sp NPs), and 22±0.79 mm to 26±0.92 mm (Au-Sp NPs) at dose of 3 mg/mL.

Multilayer for antireflection coating applications using metal nanoparticles to provide ultraviolet blocking

We propose the use of metal nanoparticles (NPs) [(silver (Ag)] embedded heterogeneous composite material made of titanium dioxide (TiO2) for antireflection coating (ARC) while partially blocking the transmission of near-ultraviolet (UV) radiation across the thin-film arrangement. The proposed structure consists of two layers of porous TiO2 thin film of specific thickness and volume fraction to attain antireflection property with Ag NPs embedded in the upper layer to optimize the UV blocking potentiality within the range of 320 to 400 nm. The calculations indicate that 10-nm Ag NPs with volume fraction of 0.01 and film thickness (51-nm top layer and 102-nm bottom layer) give the best results for blocking of near-UV radiation. Decreasing the aspect ratio of the prolate nanospheriod gives better UV blocking intensity.

Optimization of front metal contact design of Industrial Si solar cells using photoluminescence imaging technique

Abstract Silver (Ag) based front contact metallisation is a crucial process step in industrial Si solar cell fabrication. Lesser front metal coverage leads to high resistive losses, whereas higher coverage results in shadowing loss as well as increased metal-induced recombination losses. Both scenarios impede the power conversion efficiency of solar cells. Therefore, it is essential to monitor the shadow, resistive, and metal-induced recombination losses associated with the design of front Ag contact. In this work, we demonstrate the application of photoluminescence (PL) imaging technique in association with the other conventional characterization techniques used in the optimization of front contact metallisation.

Physical and photocatalytic properties of Nd codoped (Ag, Cu)TiO2 thin films

ABSTRACT Transparent co-doped TiO2 thin films have been fabricated by sol-gel dip-coating. The doping is achieved using low concentrations of neodymium (Nd), silver (Ag), and copper (Cu). A significant effect of doping is noticed on the morphology and optical properties of thin films. XRD analysis confirms the formation of a pure anatase phase with a deterioration of the crystallinity upon doping. The co-doped TiO2 thin films present larger crystallite size compared to other films. The surface roughness revealed by AFM increases from 0.9 nm for pure TiO2 up to 5 nm for doped thin films. UV-vis spectroscopy shows that the bandgap energy slightly decreased for co-doped Ag-Nd/TiO2 and Cu-Nd/TiO2. Photocatalytic degradation of MB significantly decreases upon doping. A mechanism based on combined effects of doping, annealing and nature of substrate is proposed to explain the photodegradation behaviour.

Reinforcing epoxy with Ag-decorated flower-like TiO2 nanoparticles: Structure and photocatalytic performance

The objective of this work was to synthesize silver (Ag) decorated flower-like (FL) titania (TiO2) nanoparticles and incorporate them into epoxy. The motivation was to increase the matrix-filler interlocking by FL morphology, so that mechanical durability of the surface could be preserved while photocatalytic capability was introduced to the polymer. FLTiO2 nanoparticles were synthesized by solvothermal reaction at 180 °C, for 4 h. Ag-decoration was performed by a simple solution-mixing approach using silver nitrate. 4 wt.% reinforced FLTiO2/epoxy composites were prepared w/o Ag-decoration. X-ray diffraction (XRD), scanning/transmission electron microscopy (SEM, TEM), gas adsorption (N2), Fourier-transform (FT) infrared (IR) and UV–visible spectroscopies were used to characterize the phases, morphology, surface, chemical and optical structure of the nanoparticles. Nanoparticles were composed of rutile (71%) and anatase (29%) phases and exhibited a mesoporous structure with an indirect band gap of 2.90 eV. Analysis of the nanocomposites indicated that FLTiO2 nanoparticles formed Ti–O–C linkages with epoxy at the interface and enhanced mechanical/chemical interlocking resulted in 13-fold increase in microhardness. Water sorption (WS) was not significantly affected by FLTiO2 reinforcement, but Ag-decoration increased the WS. FLTiO2/epoxy nanocomposites exhibited photocatalytic performance up to 48 h, w/o Ag-decoration. Ag-decoration enhanced the degradation rate. Each nanocomposite was reusable and was still photo-active after 3 cycles. In the overall, considering the well-known antimicrobial behavior of Ag, the synergic effect of Ag with FLTiO2 in epoxy can provide durable alternatives which require microbe/pollutant resistance in public environments.

Electrical contact performance of various electro-deposited graphene reinforced silver-based nanocomposites

Abstract Silver and silver(Ag)-graphene(Gr) nanocomposite coatings were prepared via direct current, pulse current and pulse reverse current on copper electrical contacts for evaluating electrical contact performance. The effects of the addition of Gr and current types on microstructure, crystallographic orientation, mechanical properties and electrical contact performance were investigataed via a scanning electron microscope, an X-Ray diffractometer, microhardness test device and an electrical contact test device, respectively. The addition of Gr changed the Ag surface morphology and decreased grain sizes. Moreover, the addition of Gr significantly improved arc erosion resistivity and decreased the average working temperature during the contact test. In addition, pulse current and pulse reverse current provided a significant improvement in microhardness and electrical contact erosion resistance owing to increased embedded graphene amounts in silver layers.

Novel Strategy for One-Step Production of Attenuated Ag-Containing AgCu/ZnO Antibacterial-Antifungal Nanocomposite Particles

Novel strategies have been developed to comply with Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulations to provide the same performances for antibacterial and antifungal materials. The strategy for producing composite materials by attenuating the silver (Ag) content and a one-step production technique without minimizing the antibacterial and antifungal performance was developed. In this study, attenuated spherical Ag containing spherical AgCu/ZnO nanocomposite particles have been synthesized from an aqueous solution of silver nitrate (AgNO3), copper nitrate (Cu(NO3)2 · 3H2O), and zinc nitrate (Zn(NO3)2 · 7H2O) by a facile one-step ultrasonic spray pyrolysis and hydrogen reduction (USP-HR) method. Characterization of AgCu/ZnO nanocomposite particles was carried out by various techniques such as X-ray diffraction analysis (XRD), scanning electron microscopy (FEG-SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The structural analysis showed that AgCu/ZnO nanocomposites were composed of face-centered cubic Ag, face-centered cubic Cu, and hexagonal ZnO phases. Antibacterial and antifungal properties of nanocomposite particles against Escherichia coli and Aspergillus niger were investigated by agar medium and broth medium methods. The obtained results indicate that produced nanocomposite particles possess antibacterial and antifungal properties (100%). The attenuated Ag in the AgCu/ZnO nanocomposite particles has the usage potential in different areas of the textile industry. In particular, the research on utilizing this nanocomposite in hand-made fiber production as an additive is of very high interest.

Effects of the Ionic and Nanoparticle Forms of Cu and Ag on These Metals' Bioaccumulation in the Eggs and Fry of Rainbow Trout (Oncorhynchus mykiss W.).

Nanotechnology is a rapidly growing field of science, and an increasing number of nanoproducts, including nanometals, can be found on the market. Various nanometals and the products that are manufactured based on them can help to fight bacteria and fungi, but they can also penetrate organisms and accumulate in them. This study aimed to compare the effects of two metals, silver (Ag) and copper (Cu), with known antibacterial and fungicidal properties in their ionic (AgNO3, CuSO4·5H2O) and nanoparticle (AgNPs, CuNPs) forms on rainbow trout eggs and fry. Concentrations of metals ranging from 0 to 16 mg/L were used during egg swelling for 2 h. The swelling of eggs in Cu solutions resulted in an increase in Cu content in the eggs (just like in the case of Ag); however, the changes in fry were not significant in the case of both Ag and Cu. The concentrations of these metals in eggs was greatly affected by the applied form of Ag and Cu. Because CuNPs penetrated the embryo in fish eggs at lower concentrations compared to AgNPs, it would be worth considering them for antibacterial applications during egg incubation.

Characterization of Nanoparticles for Nanomaterial Environmental Health and Safety Studies: The Physics and Metrology for Several Common Approaches

Tiered risk as sessment approaches for nanomaterial environmental health and safety (nanoEHS) require a detailed understanding of the size and the size distribution of the material being used. There are many metrological tools to choose from, each with its own strengths and weaknesses that influence the results being reported on the exact same batch of material. This review analyzes the physics and metrology in several commonly employed techniques for characterizing nanoparticle (NP) sizes and size distributions and presents how this leads to variations in the reported results. Finally, a case study applying this knowledge to measuring silver (Ag) NP systems is presented, including business-based examples for selecting high-throughput, low-cost measurement approaches for production quality control, and it validates these approaches with goldstandard techniques and statistically significant sampling plans.

Quantifying Electrocatalytic Reduction of CO2 on Twin Boundaries

Summary A protocol relying on the use of silver nanostructures with well-defined dimensions and morphologies (e.g., nanocubes and nanowires) has been developed to differentiate and quantitatively determine the atom-specific activities of different surface atoms toward catalyzing electrochemical CO2 reduction reaction (CO2RR). The atom-specific activity of the twin-boundary edges (TBEs) is comparable to (or slightly higher than) that of the single-crystal edges (SCEs) formed from the crossing of two {100} surfaces, and it is on the order of ∼16 attoampere/atom (aA/atom) toward electrochemical CO2RR. This value is more than two orders higher than the atom-specific activity of the {100} surface atoms, i.e., ∼0.1 aA/atom. The high catalytic activity of the TBEs, which represent a class of commonly existing surface defects in stable metal nanostructures with face-centered cubic lattices, is consistent with the DFT calculations, in which the bridge-type binding configuration of COOH∗ at the TBEs stabilizes this intermediate to promote overall CO2RR.

Observation of Fano resonance in silver nanocube–nanosphere dimer

In this paper, we perform a theoretical investigation of the plasmon coupling in silver (Ag) nanocube–nanosphere dimer using finite difference time domain (FDTD) technique. Due to plasmonic Fano resonance, we observe a pronounced dip in the absorption spectrum, which is induced by the destructive interference between the bright dipole mode from the Ag nanocube and the dark quadrupole mode from the Ag nanosphere. We study the effects on the Fano resonance by varying the dimensions of the nanocube and nanosphere, as well as the inter-surface gap distance between them. In addition, we vary the local dielectric environment surrounding the dimer and find a wide tuning in the Fano resonance line-shape. We calculate the localised surface plasmon resonance (LSPR) sensitivity of the nanocube–nanosphere dimer to the surrounding environment and find a high figure of merit (FOM) of 32.23, which indicates its promising potential as a plasmonic biosensor.

Electroplating Method on Copper (Cu) Substrate with Silver (Ag) Coating Applied

Knowing about metal coating (electroplating) is the electrodeposition of coatings or coatings attached to the electrodes to protect the substrate by giving surface properties and dimensions different from the base metal or finishing technique, by coating metal that is easily corroded (corrosion) with metals that are resistant to corrosion with electrical and chemical engineering. Whereas in Indonesian society the technique for metal coating is very familiar with the name of the gilding technique. In ancient times before electroplating and gilding were discovered to avoid corrosion of metals, the incorporation of metals such as copper with tin into bronze, copper with zinc into brass in addition to being resistant to corrosion also added to the beauty of color. Among the alloys above bronze is the oldest alloys that have been used by humans. With the development of the times, more modern gilding techniques were found to be a more practical method, namely electroplating, gilding with electrical and chemical processes that make metals resistant to corrosion. Metal coating is a scientific field which is one of the applications of electro chemical technology. Very closely related to the material science and technology, surface chemistry, physical chemistry, to the engineering. Various metals can be plating. The various metals are classified into five groups: "tumbal" coatings, decorative-protective coatings, engineered metal coatings, rare-use metals, and various types of alloys. All of these have their own characteristics, both advantages and disadvantages.

Initiatively embedding silver colloids in glass used in silver paste to improve metallization ohmic contact on silicon wafers

One of the decisive factors in realizing ohmic contact of silver (Ag) paste metallization on silicon (Si) wafers is the presence of Ag colloids in the glass phase at the Ag/Si interface. The Ag colloids are formed during the reaction between glass frit and Ag powder in the sintering process of Ag paste; thus, it is difficult to control the quantity of Ag colloids formed. In this study, we attempted to prepare a glass embedded with a large number of Ag colloids first to further improve the quality of ohmic contact of Ag paste metallization. In the PbO–TeO2–SiO2 glass system, a route was found for increasing the solubility of Ag in the glass melt by precipitating the Ce1.88Pb2.12O6.53 crystal, which enabled a molar amount of recrystallized Ag colloids reach a high level of about 1/10 of oxides in the glass. As a result, the resistivity of the Ag/Si contact can be decreased substantially. The formation mechanism of Ag colloids in glass is revealed by various characterization and analysis methods, such as X-ray diffraction, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, UV–visible and so on. Furthermore, it was also found that too high content of Ag in the glass melt would destroy the pyramid texture surface structure of Si wafers, which is not conducive to obtain high-quality Ag/Si ohmic contact. For this concern, optimal content of Ag colloids formed in glass is discussed.

Synthesis and Characterization of Silver Nanoparticles from <I>Ashyranthus aspera</I> Extract for Antimicrobial Activity Studies

Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving into an important branch of nanotechnology. Plant-mediated synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. In the present study, we were synthesized silver (Ag) nanoparticles using aqueous extracts of fresh leaves of Ashyranthus aspera medicinal plants as bio-reducing agents. UV-Vis spectrometer used to monitor the reduction of Ag ions and the formation of AgNPs in the medium. UV-Vis spectra and visual observation showed that the color of the fresh leaf extracts of Ashyranthus aspera turned into grayish-brown respectively, after treatment with Ag precursors. XRD and SEM have been used to investigate the morphology of prepared AgNPs. The peaks in the XRD pattern are associated with that of the Face-Centered-Cubic (FCC) form of metallic silver. TGA/DTA results associated with weight loss and exothermic reaction due to the desorption of chemisorbed water. FTIR was performed to identify the functional groups which form a layer covering AgNPs and stabilize the AgNPs in the medium. Moreover, silver nanoparticles using aqueous leaf extracts of Ashyranthus aspera were separately tested for their antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Enterobacter). The results showed that the bacterial growth was inhibited by the extracts containing AgNPs Nanoparticles. The biosynthesized nanoparticle was prepared from Ashyranthus aspera leaf extracts exhibits potential applications as broad-spectrum antimicrobial agents
 Keywords: Ashyranthus aspera, Silver Nanoparticles, Plant extracts, Bacteria, Antibacterial activity.

Antibacterial Effect of Silver Nanomaterials on Staphylococcal Protein A by Molecular Dynamics Simulation.

Nanotechnologies have changed this world in various aspects including the oral medicine. It has been demonstrated that silver (Ag) nanomaterials can exhibit strong inhibition and killing effect on oral bacteria. Furthermore, the Ag nanomaterials have superb antimicrobial activity and nonacute toxic effects on human cells. Previously, the impact of Ag on oral bacteria was demonstrated by experiments. In this work, we applied molecular dynamics (MD) simulations to investigate the influence of Ag nanomaterials on oral bacteria. Firstly, by comparing change of molecular structure of staphylococcal protein A (SPA) with and without Ag, we found that Ag nanomaterials have strong effect on evolution of protein secondary structure of SPA. Secondly, it was observed that Ag has negligible effect on Solvent Accessible Surface Area (SASA) of SPA indicating that the Ag only changed its microstructure. Finally, it was found that the average amount of hydrogen bond in SPA was reduced in the presence of Ag which was origin of antimicrobial activity of Ag. It is believed that the growing interest in dental medicine with nanomaterials would lead molecular dynamics simulations to be an effective method for studying inhibition and killing pathological process of nanomaterials on oral bacteria.

Preliminary Study of Hydrometallurgical Extraction of Silver from Selected E-Waste

Electronic relays (ER) are a type of switch which are an essential part of electronic devices used to open or close circuits by using electronic components without any mechanical operation. After decommissioning, it can be considered as an important source of base and precious metals with high economic value. The annual growth rate of about 4-5 % in 2016 is one of the fastest growing waste stream, and only about 20 % of e-waste is recycled. After the use-phase, electronic devices become electronic waste (e-waste); consequently, it is important to consider e-waste as a secondary supply for the recovery of precious metals. In this study, a simple hydrometallurgical recovery method for silver (Ag) extracting from used electronic relays was performed. The silver extractions consisted of six stages: disassembling of relays, removal of base metals, leaching in nitric acid, precipitation, conversion silver oxide and melting. Measurements of extracted precious metals were carried out by scanning electron microscope (SEM) and EDS (Energy Dispersive Spectrum) analysis. The purity rate of the final deposit was 94.9 % on the surface of the sample, and the final silver recovery yielded 0.44 % of the raw material. During the second stage of the experiment, mixed types of electronic relays were used to compare the yields. Electronic relays can be considered as an important source of base and precious metals with high economic value. The final yield of the mixed electronic relays reached up to 0.54 % of Ag with the purity of over 95 %.

Polymer-dispersant-stabilized Ag nanofluids for heat transfer applications

One-step wet chemical method has been employed for the synthesis of silver (Ag) nanofluids followed by the preparation of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and PVP–PVA mixed-dispersant-stabilized nanofluids by varying the concentration ratio of dispersants for the viscosity and thermal conductivity analysis. The optical absorption studies indicate the presence of nanoparticles in the prepared fluids (or the formation of the silver nanoparticles). The shape and size of the nanoparticles are confirmed by the field emission scanning electron microscopy, and the particle size distribution and zeta potential analysis were carried out by using dynamic light scattering. It is observed that the thermal conductivity of Ag nanofluids increases with an increase in the dispersant concentration with respect to the temperature. The maximum thermal conductivity enhancement of Ag nanofluids was observed in the presence of an equimolar ratio of PVP–PVA (1:1:1) blends as stabilizers.Graphic abstract

Influence of size, shape and dimension on glass transition and Kauzmann temperature of silver (Ag) and tantalum (Ta) nanoparticles

A simple model is developed for the investigation of size, shape and dimension dependent glass transition temperature (Tg) and Kauzmann temperature (TK) of nanoparticles. The model is based on thermodynamical quantity cohesive energy and is free from fitting parameters and approximations. To check the validity of the model, calculations on the size, shape and dimension dependent glass transition (Tg) and Kauzmann temperature (TK) are performed for silver (Ag) and tantalum (Ta) nanoparticles (NPs) of different shapes. The considered shapes are spherical, tetrahedral, octahedral and icosahedral accompanied with zero-, one- and two-dimensional geometries. Our results reveal that the Tg and TK strongly depend on the size of the nanoparticles. As the size of the NPs decreases, Tg and TK decrease. It is observed that both temperatures follow the trend as (icosahedral, D) > (spherical, D) > (octahedral, D) > (tetrahedral, D) for selected Ag and Ta nanoparticles. However, in terms of dimension, they show the d = 0 < d = 1 < d = 2 trend. The calculated values of glass transition and Kauzmann temperatures for both considered nanoparticles have good agreement with available molecular dynamics (MD) simulation and experimental data.

Horizontal gene transfer and silver nanoparticles production in a new Marinomonas strain isolated from the Antarctic psychrophilic ciliate Euplotes focardii

We isolated a novel bacterial strain from a prokaryotic consortium associated to the psychrophilic marine ciliate Euplotes focardii, endemic of the Antarctic coastal seawater. The 16S rDNA sequencing and the phylogenetic analysis revealed the close evolutionary relationship to the Antarctic marine bacterium Marinomonas sp. BSw10506 and the sub antarctic Marinomonas polaris. We named this new strain Marinomonas sp. ef1. The optimal growth temperature in LB medium was 22 °C. Whole genome sequencing and analysis showed a reduced gene loss limited to regions encoding for transposases. Additionally, five genomic islands, e.g. DNA fragments that facilitate horizontal gene transfer phenomena, were identified. Two open reading frames predicted from the genomic islands coded for enzymes belonging to the Nitro-FMN-reductase superfamily. One of these, the putative NAD(P)H nitroreductase YfkO, has been reported to be involved in the bioreduction of silver (Ag) ions and the production of silver nanoparticles (AgNPs). After the Marinomonas sp. ef1 biomass incubation with 1 mM of AgNO3 at 22 °C, we obtained AgNPs within 24 h. The AgNPs were relatively small in size (50 nm) and had a strong antimicrobial activity against twelve common nosocomial pathogenic microorganisms including Staphylococcus aureus and two Candida strains. To our knowledge, this is the first report of AgNPs biosynthesis by a Marinomonas strain. This biosynthesis may play a dual role in detoxification from silver nitrate and protection from pathogens for the bacterium and potentially for the associated ciliate. Biosynthetic AgNPs also represent a promising alternative to conventional antibiotics against common pathogens.