Ag Microparticles Research Articles

Antibacterial action of novel zeolite-based compositions depends upon doping with Ag(+) and Сu(2+) cations

Recently, there is a growing interest to exploration of sorption and catalytic properties of solid nanomaterials, in particular natural zeolites, as well as to study of their antimicrobial effects with the aim of potential using them as a principal component of disinfection and degassing remedies. The purpose of this work was to study the antimicrobial action of compositions based on the Transcarpathian clinoptilolite (CL) doped with Ag+ and Сu2+ cations or Ag microparticles (MPs). These compositions were subjected to mechanochemical modification in ethanol medium and with the addition of plant (Actinidia arguta) extract used as an antioxidant. Mechanochemical treatment (MChT) of all forms of CL MPs led to their grinding which caused better contact of CL with bacterial cells, while an increased content of larger pores improved their access to the active sites on the surface of the CL MPs. Treatment of CL samples with metallic silver used as a dopant with the help of the extract of Actinidia arguta plant did not increase the antibacterial activity regardless of treatment time. Treatment of AgNO3 with ethanol slightly increased the antibacterial action of the CL MPs towards Gram-positive bacteria and decreased it towards Gram-negative bacteria. The CL samples doped with copper and treated with ethanol and plant (Actinidia arguta) extract demonstrated comparable toxic action towards Bacillus subtilis regardless of grinding conditions. While such a treatment caused a significant decrease in the antibacterial activity towards Staphylococcus aureus and Pseudomonas aeruginosa strains, compared to the action of samples that were not treated with that plant extract. To address the potential biochemical mechanisms of the antibacterial action of the created zeolite-based compositions, their influence on generation of the reactive oxygen species (ROS) was studied using diphenylpicrylhydrazyl (DPH) fluorescent dye. Most versions of the CL composites demonstrated time-dependent antioxidant effect comparable with the effect of the ascorbic acid used as a positive control. Thus, the ROS generation is not the mechanism that is responsible for the antibacterial action of the created CL-based compositions. Probably, that action is explained by the peculiarities of interaction of doped CL microparticles with the surface of the bacterial cells. Keywords: antimicrobial action, clinoptilolite-based compositions, doping with Ag+ and Сu2+ cations, physicochemical treatment

Low toxicity of dissolved silver from silver-coated titanium dental implants to human primary osteoblast cells

Objectivesthe controlled release of silver as a biocide from Ag-coated medical implants is desirable. However, the biocompatibility of Ag leachates is poorly understood. This study investigated the toxicity of silver released from the silver plated titanium implants to human primary osteoblast cells; and the effect of cell culture medium on the silver speciation and bioavailability. Methods: Ti6Al4V discs were coated with Ag nanoparticles (NPs), silver plus hydroxyapatite (HA) nanoparticles (Ag+nHA), or Ag NPs plus microparticles (Ag+mHA). Primary human osteoblast cells were exposed to the leachates from the various discs for up to 7 days. Results: the total Ag concentrations released as leachate from the silver-plated titanium discs were 0.7–1.6 mg L−1, regardless of treatment. Cumulative silver release over 7 days was approximately 3 mg L−1 in all treatments. The concentration of total Ag in the cell homogenates from all the Ag-containing treatments was modest, ∼ 0.1 µg mg protein−1 or less at day 7. Cells showed normal healthy morphology with no appreciable leak of LDH or ALP activity into the external media compared to the reference control. Similarly, there was no significant differences (Kruskal Wallis, p > 0.05) in the LDH or ALP activity in the cell homogenate between treatments. Conclusions: overall, there was a controlled release of Ag into the external media, but this remained biocompatible with no deleterious effects on the osteoblast cells, which means that the released silver to the peri-implant environment is not toxic making the coating potential for clinical use

An Ultra-broadband Metallic Plasmonic Antenna for Ultrasensitive Molecular Fingerprint Identification.

Near-field enhanced mid-infrared light-matter interactions via metallic plasmonic antennae (PA) have attracted much attention but are inevitably limited by the detuning between their narrow band and the broad applied spectral range. Here, we develop a new low-temperature incubation synthetic method to acquire uniform Ag microparticles (MPs) with numerous hotspots. Their plasmonic band is remarkably extended by the plasmonic coupling of numerous hotspots and covers the entire mid-infrared range (400-4000 cm-1). Hence, the almost complete molecular fingerprint of 4-mercaptobenzonitrile was successfully probed for the first time via resonant surface-enhanced infrared absorption (rSEIRA), and the rSEIRA spectra of different essential amino acids were further detected and exhibit a high spectral identification degree assisted by machine learning. This work changes the inertia perception of "narrow band and large size but small hotspot area" of mid-infrared metallic PA and paves the way for the ultrasensitive mid-infrared optical sensing.

Induced ageing of ZnS:Ag microparticles exposed to 13 keV electron beam

Phosphorescent microparticles made of ZnS:Ag were exposed to pulsed electron beams with an energy of 13 keV for periods of time between 30 min and 240 min. An XRD analysis showed no modification of crystalline structure. The average cristalites of ZnS:Ag was 62 nm deduced from SEM imaging. The luminescence spectra showed a decreasing activity with 40% after 30 min of irradiation at a fluence of 5.79 ×1016 electrons/cm2. The broad peak between 445 nm to 480 nm centered aroud 460 nm with a FWHM almost constant aroud 80 nm show no shifting. After a long exposure (over 240 min) and a fluence of 4.60 ×1017 electrons/cm2, the powder suffered a blackening effect attributed to formation of dead layers under electronic excitation combined with increasing of Sulphur vacancies, quantitatively confirmed by EDS analysis, where the proportion of S in ZnS:Ag decreases from 31.42% to 13.75%. Also, the luminescence at this moment dropped to almost 90% under the electron beam effect. The thermal effect could not be correlated with luminescence quenching, which was attributed to the increase in the number of impurities.

Ag Sinter Bonding to Si Substrate via Temporal Formation and Decomposition of Ag Carboxylate.

This paper demonstrates the in situ sinter bonding of Ag microparticle pastes to a Si substrate via the temporal formation and decomposition of Ag carboxylate on the surface of Ag microparticles. This was proposed via the investigation of Ag sinter bonding using the redox reaction between Ag2O and ethylene glycol, which achieved a bonding strength above 30 MPa even for the bonding temperature at 220 °C. Thermal analysis was used to identify the product of the redox reaction between Ag2O and ethylene glycol and determine the bonding temperature because the final reaction facilitates the interfacial sinter bonding with the substrate. Fourier-transform infrared spectroscopy and nuclear magnetic resonance results indicated the in situ formation of Ag salts of carboxylic acids, such as Ag oxalate on the surface of Ag microparticles. Therefore, the sinter bonding process enabled by the in situ formation and subsequent decomposition of these Ag salts was investigated using Ag microparticles and oxalic acid. Observations of the surface and interfacial morphology of the Ag particles after heating revealed the formation of Ag nanoparticles on the surfaces of the microparticles and the formation of sintering necks between the particles. The bonding experiments demonstrated a significant increase in strength with the addition of oxalic acid to the Ag paste due to the enhanced interfacial sinter bonding with the substrate. The in situ formation and decomposition of Ag salts are promising strategies for improving sintered bonds in electronic devices because they can provide enhanced localized sinter bonding using stable insert materials.

A method for simultaneously preparing crack-based and composite-based PDMS strain sensors by mixing AgNWs and Ag microparticles

Resistive-type strain sensors have been widely studied because of their high precision and convenient measurement. But the high sensitivity and large strain range of this kind of sensor conflict with each other. It is difficult to prepare a sensor with high sensitivity and a large tensile range at the same time. Here, we propose a method to use AgNWs/Ag microparticles (AgMPs) and PDMS to simultaneously manufacture two strain sensors with different principles, a crack-based sensor and a composite-based sensor. On the one hand, the crack-based sensor has a low detection limit of 0.5% strain and high sensitivity of GF ≈ 90 at the strain of 0 ∼ 50%. It is suitable for the detection of small strains and can detect throat vibration when speaking. On the other hand, the composite-based sensor has a large strain range of 0 ∼ 240% and excellent stability. After 1000 cycles of stretching-releasing at 50% strain, the resistance change rate remains unchanged. It is suitable for the detection of large strains. Moreover, the sensitivity and working range of the composite-based sensor can be adjusted by changing the ratio and total amount of AgNWs/AgMPs composites. It can accurately monitor the different bending angles of the elbow joint and a people’s walking status and pace. The strain sensor prepared by this method has great practical value in wearable devices and electronic skin.

Synthesis of ZnO/MoS2 heterojunction with the green Ag nanoparticles for the efficient sunlight photocatalytic activity

Pristine MoS2 nanosheet/silver nanoparticles (MoS2/Ag NPs) and composites are fabricated via hydrothermal, green synthesis, and chemical methods. Pristine MoS2, Ag, Z/M, and Z/M/Ag nanoparticles and composites are characterized through SEM, FTIR, as well as UV–Vis spectroscopy. The bandgap of materials is reduced effectively which is useful for photocatalytic activity. The photocatalytic decomposition of pharmaceutical drugs in effluent has been researched using metal-oxide or metal-sulfide-based semiconductor nanoparticles as nano-catalysts. The originality of these nano-catalyst substances lies in their relative simplicity of manufacturing, capacity to absorb energy in the UV–visible spectrum, large bandgap, innoxious, and inexpensive. The visible-light photocatalytic activity of Z/M also Z/M/Ag composites were investigated using a test of OTC. Almost degradation of OTC in about 120 min. at different concentrations of composites, Z/M/Ag photocatalyst was attained. This substantial enhancement in the photocatalytic proficiency of Z/M/Ag photo-catalyst below visible light ir-radiation may be ascribed to existence of MoS2 and Ag micro-particles on ZnO micro-particles which significantly improves absorption in an observable scale of the visible range.

Probing the Conductive and Tribological Behaviors of Solid Additives in Multiply Alkylated Cyclopentanes for Sliding Electrical Contact.

Sliding electrical contacts need to be lubricated by conductive lubricants to perform low energy dissipation, high reliability, and long service life. This work studied the thermal stability, anti-corrosion capacity, and conductive, and tribological behaviors of several solid additives in multiply alkylated cyclopentanes (MACs), including carbon nanotubes (CNTs), multilayer graphene (MG), and silver microparticles. The results showed that all the additives possessed favorable thermal stability and corrosion resistance; in particular, CNTs and MG exhibited lower and more stable electrical contact resistance (ECR) and better lubricity abilities than Ag microparticles. Moreover, based on the characterization of the worn surfaces and the film thickness calculation, the favorable conductive and tribological properties of CNTs and MG were related to the high conductivity and specific structure of the additives and the good chemical inertness of MACs.

Immobilization of gaseous elemental mercury by Ag nanoparticles: A combined DFT and experimental study

Silver nanoparticles (AgNPs) have attracted considerable attention as promising industrial adsorbents of gaseous mercury. The underlying mechanism of immobilization of Hg0 on different AgNP surfaces was investigated in theoretical and experimental approaches. The crystallographic properties of AgNPs obtained by X-ray diffraction and selected area electron diffraction were incorporated into comparative DFT calculations to evaluate the adsorption energy on AgNP surfaces such as low-index and edge planes. In addition, the energy pathway of oxidation of adsorbed Hg to HgO on AgNP surfaces was analysed by an ab-initio method, which suggested chemisorption rather than catalytic oxidation to be the main mechanism of mercury removal by AgNPs in the low-to-middle temperature range (≤326 °C). Mercury adsorption and desorption tests were conducted in a fixed-bed reactor with Ag nanoparticles and microparticles as adsorbent, where AgNPs were more efficient than microparticles in mercury removal, and the removal efficiency remained stable after four rounds of regeneration. Furthermore, temperature-programmed desorption analysis suggested a second-order desorption of Hg from AgNPs with an activation energy of 0.84 eV. X-ray photoelectron spectroscopy showed that the chemical characteristics of AgNPs remained stable while adsorbing Hg0 and that the adsorbed Hg was not in an oxidation state, validating the DFT results. By providing an integrated understanding of mercury adsorption on AgNPs, these computational and experimental results will help to guide the design and optimisation of Ag-based mercury adsorbents for industrial applications.

Stability and viability of synbiotic microgels incorporated into liquid, Greek and frozen yogurts.

The viability of Lactobacillus acidophilus when co-encapsulated with fructooligosaccharides in alginate-gelatin microgels, for incorporation into liquid, Greek, and frozen yogurts, during storage and in vitro-simulated digestion was studied. Liquid yogurt provided the highest viability for the encapsulated probiotics during storage, followed by frozen and Greek formulations when compared to free probiotics, highlighting the influence of microencapsulation, yogurt composition, and storage conditions. Addition of up to 20% of probiotic (AG) and symbiotic (AGF) microgels did not cause significant changes in the liquid and frozen yogurts' apparent viscosity (ηap ); however, it decreased ηap for the Greek yogurt, indicating that microgels can alter product acceptability in this case. Both AG and AGF microparticles improved viability of cells face to gastric conditions for liquid and frozen yogurts, delivering cells in the enteric stage. Summarizing, liquid yogurt was the most appropriate for probiotic viability during storage, while frozen yogurt presented better protection along digestibility.

Optimized colloidal growth of hexagonal close-packed Ag microparticles and their stability under catalytic conditions

The colloidal synthesis of hcp silver microparticles is optimized by tuning the chemical reduction kinetics and the surface stabilization during synthesis.

Antibacterial properties and cytocompatibility of Ti-20Zr-10Nb-4Ta alloy surface with Ag microparticles by laser treatment

In order to improve the antibacterial behavior of Ti-20Zr-10Nb-4Ta (TZNT) alloy, Ag, with broad-spectrum antibacterial properties, was introduced on the surface of TZNT using a simple and efficient laser surface modification method. After laser treatment of TZNT alloy covered by Ag foil, Ag microparticles were successfully formed on the surface. The SEM, EDS, 3D topography and XRD were investigated to prove the presence of Ag microparticles. The characteristic peaks of cubic silver crystal were observed in XRD results. The Ag2O film on the surface of Ag microparticles was confirmed by XPS. The contact angel tests show that laser60 and laser70 TZNT alloys possess better hydrophilic character and higher free surface energy, compared with untreated TZNT. All laser-treated TZNT alloys reveal a higher OCP, Ecorr and Rct than untreated TZNT. However, a larger corrosion rate and a lower Rf are concluded for laser-treated TZNT alloys due to the influence of Ag microparticles. The results of in vitro antibacterial and cytocompatibility experiments indicate that Ag microparticles exhibit high antibacterial property (with a 96.3% minimum antibacterial rate) against both E. coli and S. aureus and good cytocompatibility with MC3T3-E1. This research presents a simple and efficient laser surface modification method for improving antibacterial resistance of titanium implant surface, which has a good application prospect in orthopaedic field.

Multivariate Correlation Analysis of the Electroconductive Textiles Obtained Using Functionalization by Radio-Frequency Oxygen Plasma Treatments.

This paper presents a study concerning the preliminary treatments in radiofrequency (RF)oxygen (O2) plasma used to obtain a hydrophilic effect on raw cotton fabrics followed by electroconductive thin film deposition to obtain electroconductive textile surfaces. In addition, this study presents a multivariate correlation analysis of experimental parameters. The treatment using RF plasma O2 aimed to increase the hydrophilic character of the raw fabric and adherence of paste-based polymeric on polyvinyl alcohol (PVA) matrix and nickel (Ni), silver (Ag) or copper (Cu) microparticles. The purpose of the research was to develop electroconductive textiles for flexible electrodes, smart materials using a clean technology such as radiofrequency (RF) plasma O2 to obtain a hydrophilic surface with zero wastewater and reduced chemicals and carbon footprint. To achieve the foreseen results, we used advanced functionalization technologies such as RF plasma O2, followed by scraping a thin film of conductive paste-based Ni, Ag or Cu microparticles, and multivariate correlation methods to observe the dependence between parameters involved (dependent and independent variables). Overall, the fabrics treated in plasma with O2 using a kHz or MHz generator and power 100–200 W present an excellent hydrophilic character obtained in 3 min. After RF O2 plasma functionalization, a thin film based on polymeric matrix PVA and Ni microparticles have been deposited on the fabric surface to obtain electroconductive materials.

Fabrication of Ag micro-particles based on stress-induced migration by using multilayered structure with artificial holes array.

Silver micro/nanomaterials have attracted a great deal of attention due to their superior physicochemical properties. The atomic migration driven by electromigration or stress-induced migration has been demonstrated to be a promising method for the fabrication of metallic micro-/nanomaterials because of the advantage of simple processing. However, how to realize the controllable fabrication and mass production is still the critical technical problem for the method to be used in large-scale industrial applications. In this paper, the multilayered samples consisted of copper foil substrate, Ti adhesive layer, Ag film, and TiN passivation layer and with arrays of artificial holes on the passivation layer were applied to prepare arrays of Ag micro-particles. For the purpose of controllable fabrication, stress-induced migration experiments combined with finite element simulation were applied to analyze the influence of the passivation layer thickness and the heating temperature on the atom migration and Ag particles growing behavior. And the relationship between size of the fabricated Ag particles and the processing parameters of stress-induced migration experiments were also investigated. As a result, a proper structure size of the multilayered samples and heating temperature were recommended, which can be used for the Ag micro-particles controllable fabrication and mass production.

A simple platform for the electro-catalytic detection of the dimetridazole using an electrochemical sensor fabricated by electro-deposition of Ag on carbon graphite: application: orange juice, tomato juice and tap water

The objective of this paper is to evaluate and optimize the experimental parameters of the electro-deposition of silver atom nuclei on a graphite carbon paste to elaborate an electrochemical sensor. The electro-deposition process was performed using the cyclic voltammetry. The electrochemical studies show that the deposited silver micro-particle array offers an excellent electro-catalytic activity towards the NO2 attractor group of the dimetridazole side chain. SEM morphological analysis of the silver deposits indicates the presence of a large number of Ag micro-particles on the graphite carbon with good nucleation. The size of the Ag micro-particles is of the order of 19,7621 μm and their distribution is normal over the entire range of the pulp. DRX analysis of the deposit also indicates that the microcrystalline structure of the silver microcrystals in the deposit is face-centered cubic. The electrochemical behavior of dimetridazole is totally irreversible, the transfer process is controlled by diffusion phenomena on the surface of the electrode covered by a silver deposit realized μAg@CPE. The analytical performance of the constructed electrode shows a good selectivity. Calibration curves for the detection of dimetridazole have been drawn in the concentration range of 3,5 × 10−4 mol/L to 10−6 mol/L using cyclic voltammetry method, with a detection and quantification limits of 6.565 × 10−7 mol/L and 2.216 × 10−6 mol/L respectively. The applicability of the constructed electrode has been tested in real samples including orange juice, tomato juice, tap water. The results obtained show a recovery rate above 94%, which is very satisfactory.

Probing the Ag – liquid gallium system and its interaction with redox active solutions for catalysis and AgTCNQ formation

The creation of liquid metal alloys that are reacted with species in solution is a relatively new approach to the synthesis of functional nanomaterials. In this work we explore the liquid Ag–Ga system and its interaction with redox active species in aqueous solution in the areas of heterogeneous catalysis and charge transfer complex formation. It was found that when Ag is alloyed with Ga that solid microwires of Ag2Ga were formed over time with a width of ca. 1–1.5 µm of up to 160 µm in length. This Ga/Ag2Ga composite was then investigated for the discolouration of methylene blue dye in both the liquid and solid state where little difference in activity was found resulting in 40% discolouration after 30 min. However, if nitrogen gas was passed through the liquid form of the catalyst the conversion efficiency of the catalyst increased significantly up to 99% after 1 min and could be re-used for up to 10 cycles. In addition, the catalytic conversion of 4-nitrophenol to 4-aminophenol at the liquid Ga/Ag2Ga catalyst was significantly greater than liquid Ga and could be reused for up to 5 cycles. The interaction of liquid Ag–Ga with the well-known electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) was also studied where it was found that a reaction only occurred immediately after mixing Ag microparticles with liquid Ga and before any Ag2Ga microwires were formed. The reaction conditions of bubbling nitrogen gas through the liquid Ag–Ga catalysts in an acetonitrile solution of TCNQ resulted in the time dependent formation of various morphologies of the semi-conducting charge transfer complex AgTCNQ. This work shows that alloying metals with Ga can result in the time dependent formation of a variety of materials under different reaction conditions when exposed to solution based redox active species.

Large-Scale Rapid Laser Sintering of Highly Stretchable Electrodes Using a Homogenized Rectangular Laser Beam.

This study explored the feasibility of a fast and uniform large-scale laser sintering method for sintering stretchable electrodes. A homogenized rectangular infrared (IR) laser with a wavelength of 980 nm was used in the sintering process. A highly stretchable composite electrode was fabricated using silver (Ag) microparticles and Ag flakes as the fillers and polyester resin as the binder on the polyurethane substrate. This laser-sintering method showed a sintering time of 1 sec and a very uniform temperature across the surface, resulting in enhancing the conductivity and stretchability of the electrodes. The effects of the laser power on the electrical and electromechanical properties of the electrodes were investigated. Using stretching, bending, and twisting tests, the feasibility of the laser-sintered stretchable electrodes was comprehensively examined. The electrode that was sintered at a laser power of 50 W exhibited superior stretchability at a strain of 210%, high mechanical endurance of 1,000 repeated cycles, and excellent adhesion. The stretchable electrodes showed excellent bendability and twistability in which the electrodes can be bent up to 1 mm and twisted up to 90° without any damage; thus, they are highly applicable as stretchable electrodes for wearable electronics. Additionally, the Ag composites were explored for use in a radio-frequency (RF) stretchable antenna to confirm the application of the laser-sintering method for stretchable and wearable electronic devices. The stretchable dipole antenna showed an excellent radiation efficiency of 95% and a highly stable operation, even when stretched to 90% strain.

Mechanical and microstructural enhancements of Ag microparticle-sintered joint by ultrasonic vibration

Silver (Ag) microparticle sintering bonding is a promising die-attach method for power device packaging. In this study, an ultrasonic-assisted bonding method that bonds chestnut-burr-like Ag microparticles rapidly at low temperatures is reported. Robust joints with an average shear strength of 36.2 MPa were achieved under ~ 240 °C (actual) 7 MPa in 300 s. Based on characterization of sintered microstructures obtained with different ultrasonic time and power, effects of the ultrasonic vibration were studied. Two unique microstructures, microbridges and dense layers, were generated with the ultrasonic vibration. The former achieved microparticle sintering, and the latter changed fracture mode of the joints from brittle interfacial debonding to ductile fracture. The results indicate the microbridges and dense layers enhanced the joints within a certain range and are generated due to crystallization driven by localized plastic deformation and localized high temperatures.

Hybrid porous silicon/green synthetized Ag microparticles as potential carries for Ag nanoparticles and drug delivery.

In the present work, the fabrication of hybrid porous silicon/green synthetized Ag microparticles was shown and the potential use as carriers for Ag nanoparticles and drug delivery was explored. Hybrid microparticles were fabricated by incorporating green synthetized Ag nanoparticles into porous silicon matrix. The main physicochemical characteristics of the hybrid systems were studied by several techniques including UV-vis spectroscopy, TEM, SEM, XRD and XPS. The toxicology of these hybrid systems was investigated by cell viability, MTT, and comet assays. In addition, the possibility to aggregate different drug to use as drug delivery system was demonstrated by using florfenicol as drug model, due to its importance in salmon industry. The experimental results showed the potential to use these hybrid systems as carries for drug delivery in salmon industry.

Three-component working electrode micron-sized Ag particles/tiO2 layer/Ti: template electrochemical synthesis and potential use as electrochemical sensor for glutathione detection

In the present work the possibility is considered of a chemical sensor synthesis for quantitative glutathione (GSH) determination. Sensor is based on a composite working electrode containing an array of micron-sized Ag particles immobilized on a conductive substrate (Ti) coated by dielectric TiO2 film. To determine GSH in biological fluids, particularly, in saliva, electrochemical silver-based sensors can be used, since such sensors contain –SH group. With the use of cyclic voltammetry (CV) with a composite working electrode containing an Ag microparticles array, the threshold of quantitative GSH determination is reduced to nM level. Since other modern analogues are inferior at least one order of magnitude in the limit of quantitative GSH detection, we assume that the proposed sensor may be of great interest for clinical diagnosis.