Ag Particle Size Research Articles

Oxygen reduction reaction on Ag nanocatalysts prepared by the microemulsion method

The microemulsion (water-in-oil) method is used to prepare novel silver catalysts onto three different carbon supports (multi-walled carbon nanotubes (MWCNT), mesoporous carbon (MC) and Vulcan carbon (C)). It allows to control the Ag particle growth and produces particles that range between 2 and 3 nm. The Ag-based catalysts are characterised by scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS). The electrocatalytic activity towards the oxygen reduction reaction (ORR) in 0.1 M KOH is studied using the rotating disc electrode method. High-angle annular dark-field (HAADF) STEM images reveal the Ag particle size range between 1.8 and 2.4 nm, and the EDS mapping shows uniform Ag distribution on the substrates used. Ag1/MC (two-step synthesis) and Ag2/MC (one-step synthesis) catalysts prepared onto the MC support show the highest mass activity of 30–37 A g−1. The two-step synthesis method is preferred to prepare Ag/MWCNT and Ag/C catalysts. The mass activity of the Ag1/MWCNT catalyst is more than two times higher than that of Ag2/MWCNT. Ag1/MWCNT shows the highest electrochemical stability after the accelerated durability test, with only a 6 mV shift in half-wave potential. The microemulsion method is very promising for the production of highly stable Ag-based catalysts with Ag particles smaller than 3 nm in size.

Modulating Silver Performance in Electrocatalytic Oxidation of HCHO via SMSI between Ag-Co3O4 Interfaces.

The replacement of oxygen evolution reactions with organic molecule oxidation reactions to enable energy-efficient hydrogen production has been a subject of interest. However, further reducing reaction energy consumption and releasing hydrogen from organic molecules continue to pose significant challenges. Herein, a strategy is proposed to produce hydrogen and formic acid from formaldehyde using Ag/Co3O4 interface catalysts at the anode. The key to improving the performance of Ag-based catalysts for formaldehyde oxidation lies in the strong SMSI achieved through the well-designed "spontaneous redox reaction" between Ag and Co3O4 precursors. Nano-sized Ag particles are uniformly dispersed on Co3O4 nanosheets, and electron-deficient Agδ+ are formed by the SMSI between Ag and Co3O4. Ag/Co3O4 demonstrates exceptional formaldehyde oxidation activity at low potentials of 0.32V versus RHE and 0.65V versus RHE, achieving current densities of 10 and 100mA cm-2, respectively. The electrolyzer "Ag/Co3O4||20% Pt/C" achieves over 195% hydrogen efficiency and over 98% formic acid selectivity, maintaining stable operation for 60 hours. This work not only presents a novel approach to precisely modulate Ag particle size and interface electronic structure via SMSI, but also provides a promising approach to efficient and energy-saving hydrogen production and the transformation of harmful formaldehyde.

Monitoring the Dynamics of the Galvanic Replacement Reaction to Develop Free-Standing Electrocatalysts

Hydrogen (H2) is well-known for its potential to become the future fuel and bring a more sustainable energy system [1]. The selective electrooxidation of organic compounds from biomass appears to be a possible substitute for the kinetically slow oxygen evolution reaction (OER) at the anode, which increases the electrical energy input for a conventional water electrolysis in alkaline media [2]. However, this approach is currently impeded by limited fundamental knowledge of the different active sites of electrocatalysts. The latter can be used to control selectivity at low potential and high current density to co-generate value-added products at the anode instead of CO2 by complete oxidation. Nanostructured gold-based multi-metal electrocatalysts can meet such objectives. Particularly in the electro-valorization of cellulosic biomass at electrode potentials unfavorable to C-C bond breaking and high overall cell voltage.To develop such electrocatalysts, we have initiated a multivariate methodology to study the dynamics of galvanic replacement between silver and gold. This procedure allows us to control nanoporosity and nanoalloying in the resulting gas diffusion electrode (GDE): GDE-Ag1-xAux. GDE-Ag represents the electrode upon which Ag particles were electrochemically grown prior to reaction with Au(III). Thermodynamically, silver with E°(Ag+/Ag) = 0.8 V vs SHE (standard hydrogen electrode) can be replaced by gold with E°(AuCl4 –/Au) = 1.0 V vs SHE according to: 3Ag + xKAuCl4(aq) → 3xAgCl + xKCl + Ag3-3xAux.[2,3] From a kinetic point of view, the challenge is to capture in real time the formation of metal cages of Ag-Au alloys after a '3by1' atomic exchange that introduces nanoporosity and electronic strain as silver and gold have a similar atomic radius. To interrogate the driving force behind this redox process, we have also established an electrochemical methodology to extract quantitative data, allowing detailed capture of the mixed electrochemical and mass transport (diffusion) kinetics. As the precipitation product AgCl leads to pore fouling, we have developed an efficient methodology to trigger its instant dissolution as soon as it is formed, thus promoting the production of a high-quality alloy. As shown in Figure 1, upon injection of a KAuCl4 solution into a degassed solution in contact with the GDE-Ag electrode, the open circuit potential (OCP) begins to change. This evolution is due to the modification of the electrochemical interface as silver atoms are progressively replaced by gold atoms. Thereby, leading to a regulated potential defined either by the Ag(I)/Ag redox couple, or by the Au(III)/Au pair. Interestingly, we found that the OCP variation logically depends on initial conditions such as Ag loading on the GDE, KAuCl4 concentration, Ag particle size, etc. This fundamental knowledge has led to the synthesis of efficient electrocatalysts for the oxidation of cellulose subunits in alkaline media with an onset electrode potential much lower than OER (E < 1 V vs RHE (reversible hydrogen electrode)). Indeed, the formation of an alloy phase, the creation of nanoporosity within it and the free-standing nature amplify, through synergistic and electronic effects, the electrocatalytic efficiency. Acknowledgments This work was funded by French National Research Agency (ANR-22-CE43-0004).

Cost-Effective Microfabricated Silver-Based Paper Cathodes for High-Discharge-Rate Aluminum-Air Batteries

We report a cost-effective microfabricated silver-based air-cathode for high-discharge-rate aluminum-air batteries which are suitable for micro-drone applications. A challenge for batteries for aerial drones is that both high gravimetric energy density and power density are required for extended operation. While air batteries can address the energy density issue, achieving high power density necessitates high loadings of expensive catalytic materials such as platinum (Pt), which can constitute over 99% of the cost in commercial air batteries. [1] Building upon prior research that studied the power performance of an aluminum-air battery (AAB) system with a silver-based cathode, this study further explores the influence of silver (Ag) sputtering conditions and Ag loadings on AAB power performance. [2]The power performance of AAB is significantly influenced by both air flux through the air cathode and electrochemically active catalyst surface area ratio (ECSA). The ECSA is the ratio of the electrochemically active catalyst surface area to its cathode area. Sputtered Ag cathodes with catalyst loadings ranging from 0.03 mg-Ag/cm2 to 0.3 mg-Ag/cm2 consistently show high porosity, indicating good air flux for the microfabricated cathode. Increasing the loading of the sputtered Ag catalyst further can lead to particle agglomeration. To improve power performance and ECSA, a silver-copper (AgCu) co-sputtering technique has been developed, significantly increasing the surface area and power performance.Figure 1 shows cathodes with Ag loadings ranging from 0.038 mg-Ag/cm2 to 0.267 mg-Ag/cm2 under two silver sputtering conditions: 400W+5mTorr and 100W+10mTorr. Within the examined range, the latter sputtering condition shows superior power performance compared to the former. For Ag loadings exceeding 0.1 mg-Ag/cm2, both conditions show decreasing power performance as Ag loading increases, and the 100W+10mTorr curve shows a maximum power at 0.088 mg-Ag/cm2. Figure 2 shows SEM images of 0.038 mg-Ag/cm2, 0.088 mg-Ag/cm2, and 0.19 mg-Ag/cm2 films, using the 100W+10mTorr sputtering condition. Ag particle size increases with higher Ag loading, which can result from particle agglomeration. Figure 3 shows the catalyst layer porosity and the ECSA calculated from the SEM images. All samples show porosity over 90%, indicating good air flux for the microfabricated Ag cathode. The trend of ECSA for different Ag loading correlates well with the power performance, suggesting that the power performance of the microfabricated Ag cathode primarily depends on the ECSA.Further enhancement of the ECSA through AgCu co-deposition is investigated, involving two parent alloy compositions (at%): Ag28Cu72 and Ag16Cu84. Following the co-sputtering, the parent alloy undergoes selective etching of Cu using hydrochloric acid (HCl). Figure 4 compares power performance between Ag28Cu72 and Ag16Cu84. Both curves exhibit an upward trend as the silver loading increases from 0.09 mg-Ag/cm2 to 0.4 mg-Ag/cm2, with Ag28Cu72 samples showing superior power performance. Figure 5 shows an SEM image of Ag28Cu72 parent alloy with 0.32 mg-Ag/cm2 loading after Cu etching, demonstrating that the ECSA increased to 47.52 while maintaining a high porosity of 90.2%. The peak power of Ag28Cu72 0.32 mg-Ag/cm2 sample is increased to 200 mW/cm2. By comparison, a 4mg-Pt/cm2 commercial cathode shows a peak power of 280 mW/cm2.Figure 6 compares the discharge performance of the 0.088 mg-Ag/cm2 cathode with a commercial 4 mg-Pt/cm2 cathode. Both cells can discharge under 1.1 Amp with a power density exceeding 500 W/kgbattery, a threshold sufficient to lift a quadrotor drone. [3] Battery weight encompasses anode, cathode, electrolyte and battery packaging. The 0.088 mg-Ag/cm2 cathode shows a discharge power plateau above 600 W/kgbattery (86% of the 4 mg-Pt/cm2) and an energy density of 228 Wh/kgbattery when discharge power density exceeding 500 W/kgbattery (95% of the 4 mg-Pt/cm2). Remarkably, the material cost of the 0.088 mg-Ag/cm2 cathode is 5000 times less than the 4 mg-Pt/cm2 cathode.

How to design plasmonic Ag/SrTiO3 nanocomposites as efficient photocatalyst: Theoretical insight and experimental validation

An integrated theoretical-experimental investigation is performed to understand the photocatalytic and optical properties of Ag/SrTiO3 nanocomposite (Ag/STO). Theoretical investigation reveals that the catalytic activity of Ag/STO is increased when Ag particle size is smaller, while the opposite correlation is observed for its visible-light absorbance efficiency. These insights suggest that efficient Ag/STO photocatalyst needs to be balanced between the active interfacial site density and visible-light absorbance intensity by carefully controlling the Ag dosage. Furthermore, reactive oxygen species that are responsible for the oxidative degradation of organic pollutant on Ag/STO could be identified from Density Functional Theory (DFT) calculations. Comprehensive experiments are carried out using Rhodamine-B (RhB) photodegradation to test the activity of Ag/STO in wastewater treatment application and excellently validate those theoretical predictions. Over series of synthesized Ag/STO composites with different Ag contents, the optimum 1 % wt. Ag loading has the highest 92.8 % efficiency in RhB photodegradation after 1 hour of light irradiation. Trapping experiments also confirm the crucial role of O2 and OH species, which was predicted from DFT calculations, as the primary oxidizing agents for the degradation of RhB. This work provides a useful framework to develop novel plasmonic nanocomposites for other photocatalytic applications.

The role of chlorine promoters in mediating particle size effects in silver-catalyzed ethylene epoxidation

Measured chlorine coverages over Ag/α-Al2O3 catalysts with varying Ag weight loadings (1.3–35 wt%) and different Ag particle size distributions when parsed in terms of Cl coverages over particles of varying size constituted in the distribution reveal that Ag particles of size below ∼30 nm are covered in more than 1 monolayer (ML) of chlorine in presence of 3.5 ppm C2H5Cl. These assessments of Cl coverages were made possible by correlating the cumulative Cl coverage to the lognormal surface area distribution of 22 Ag/α-Al2O3 samples using a single exponential decay function. Fully chlorided small Ag particles exhibit low rates of epoxidation and only large Ag particles which exhibit sub-monolayer Cl coverages catalyze ethylene epoxidation with high ethylene oxide (EO) rates and selectivity. The Ag particle size dependence of Cl coverages plausibly explains why ≥ 100 nm Ag particles are typical in promoted Ag/α-Al2O3 ethylene epoxidation catalysts.

Exploring the influence of Ag nanocube size on surface plasmon resonance assisted photocatalytic H2-production of optimized Ag loaded TiO2

Ag nanocubes decorated plasmonic TiO2 were synthesized by polyol method as a potential photocatalyst for photocatalytic hydrogen evolution. In this work, the Ag loading concentration on TiO2 was optimized for enhanced photocatalytic hydrogen evolution. Among different Ag loading, 1 wt% showed the highest hydrogen production capacity under solar irradiation due to elevated photon absorption in the presence of plasmonic Ag. Further, the influence of surface plasmon resonance of Ag nanocubes on TiO2 was also studied by tuning the Ag particle size and evaluating the photocatalytic hydrogen production under optimized Ag loading. The size of the Ag nanoparticles was varied using different molecular weight (Mw) PVPs as the size-directing agent. TEM analyses of the samples confirmed the formation of Ag nanocubes of various sizes in accordance with the PVPs used. Ag nanocube with a size of 15.98 nm showed the highest SPR effect, which enables higher photon absorption and could generate high photogenerated charge carriers for better photocatalytic reactions. The photocatalytic hydrogen production capacity of the above samples was evaluated under solar irradiation, and the sample with an Ag nanocube size of 15.98 nm showed a yield of 4258.40 μmol g-1 in 4 h, which is 12-fold higher than its pristine counterpart. This work illustrated the effect of Ag nanocube size for effective SPR and the transportation of this high energy towards host TiO2 for enhanced photocatalytic performance.

Synthesis, Characterization, and Cytotoxicity Evaluations of Silver–Zeolite Nanocomposite

Zeolites of natural origin are materials exhibiting many positive effects on the human body. Silver-modified zeolites have already been introduced as bactericidal agents, although studies dealing with their toxicity are insufficient. This work describes the synthesis of activated and silver-loaded Bulgarian zeolite using a simple wet impregnation method. Morphological characteristics and compositions of natural zeolite, activated zeolite, and Ag-nanocomposites were studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. Silver loading is approximately 13 wt. %, with mean Ag particle size around 19 nm. Analyses of the samples included antioxidant activity assays based on ABTS radical scavenging ability and in vitro cytotoxicity tests with human normal fibroblasts and three adenocarcinoma cell lines. The experiments were performed with natural, activated, and Ag-modified zeolite in comparison to two commercial food supplements. Our results indicated moderate antioxidant activity of the tested samples. Silver-modified zeolite demonstrated cytotoxic effects against both tumor cells and normal fibroblasts, but the detected levels of inhibition were stronger against the adenocarcinoma cells, suggesting anti-tumor potential. The present article indicates a new aspect of Bulgarian natural zeolite and Ag-loaded zeolite biological activity. It highlights the need for detailed toxicity evaluations of Ag-nanocomposites prior to healthcare applications.

Insight into the size-dependent activity in Ag/SiO2 catalyzed hydrogenation of dimethyl oxalate to methyl glycolate

Methyl glycolate (MG) is an important building block for synthesizing biodegradable material of polyglycolic acid. Hydrogenation of coal-based dimethyl oxalate (DMO) to MG is quite promising, where Ag-based catalysts exhibited excellent selectivity. Here, a series of Ag/SiO2-x catalysts with particle sizes of 1.4–13.5 nm were prepared, which showed significant structural sensitivity in DMO hydrogenation. For Ag nanoparticles of 1.4–2.7 nm, the turnover frequency (TOF) was linearly increased with the surface electron density of silver, but when the Ag nanoparticles further enlarged, no significant variation of TOF was observed. Combining DFT calculation and experimental results of the model catalyst, triangular nanoplate, it was deduced that the Ag (111) played a dominant role in DMO hydrogenation to MG, originating from the benefited MG desorption as well as promoted dissociation of H2 and DMO. This understanding about Ag particle size effect may provide guidance for designing efficient catalysts for DMO hydrogenation to MG.

High enhancement, low cost, large area surface enhanced Raman scattering substrates all by atomic layer deposition on porous filter paper

We successfully developed an atomic layer deposition (ALD) method for making Ag noble nanoparticles on cheap, commercial filter paper consisting of three-dimensional porous glass fibers and investigated the evolution of Ag nanostructures with some key process parameters. By tuning Ag particle sizes and controlling the cycle numbers of ALD deposited Ag films, we were able to obtain high-density isolated Ag nanoparticles with average sizes in 3–9 nm without the formation of agglomerates and continuous Ag films. We proved the presence of strong localized surface plasmon resonance peaks near a target wavelength of 632 nm. We further proved the presence of surface enhanced Raman scattering (SERS) signals on the Ag coated filter paper substrates using pyridine as the test analyte. Our results demonstrate that ALD is a very promising technique for a rational design of SERS substrates and, thus, has great potential for the fabrication of large-area, low-cost SERS substrates for future commercial applications, as compared to other existing techniques.

Fabrication of silica/calcium alginate nanocomposite based on rice husk ash for efficient adsorption of phenol from water.

The current work discusses the synthesis of three different solid adsorbents: silica nanoparticles derived from rice husk (RS), calcium alginate beads (AG), and silica/alginate nanocomposite (RSG). The fabricated solid adsorbents were characterized by using different physicochemical techniques such as TGA, XRD, nitrogen adsorption/desorption analysis, ATR-FTIR, pHPZC, SEM, and TEM. The adsorption efficiencies of the prepared solid adsorbents were considered for the removal of phenol as a selected hazardous pollutant. Because of its improved adsorption capacity and environmentally friendly character, a composite made of biosilica nanoparticles and naturally occurring alginate biopolymer by click chemistry is significant in environmental treatment. Adding silica nanoparticles to the alginate biopolymer hydrogel has many advantages, including increased surface area, easier recovery of the solid adsorbent, and additional surface chemical functional groups. The silica/alginate nanocomposite showed surface heterogeneity with many chemical functional groups present, whereas silica nanoparticles had the highest surface area (893.1 m2 g-1). It has been found that the average TEM particle size of RS, AG, and RSG was between 18 and 82 nm. RSG displayed the maximum adsorption capacity of phenol (100.55 mg g-1) at pH 7 and 120 min as equilibrium adsorption time. Adsorption of phenol onto the solid adsorbents fit well with a nonlinear Langmuir isotherm with favorable adsorption. Kinetic and thermodynamic studies prove that the adsorption process follows a pseudo-second-order kinetic model, endothermic process, physical, and spontaneous adsorption. Sodium hydroxide is effective in desorbing 94% of the loaded phenols, according to desorption investigations. Solid reusability tests showed that, after seven cycles of phenol adsorption/desorption, RSG lost only 8.8% of its adsorption activity.

Influence of Ag particle size and Ag : Al2O3 surface ratio in catalysts for the chloride-promoted ethylene epoxidation

Ethylene epoxidation is catalyzed by α-alumina supported silver catalysts. The influence of silver particle size has been a topic of debate, and was typically investigated without the industrially essential chloride promoter. We studied the catalyst behavior in the presence of chloride. Transient behavior was observed in the first tens of hours on stream, not as a result of particle growth, but due to the gradual change in the nature of the active silver site in the presence of chloride. Different strategies were used to tune the particle size: either varying the silver loading or varying the decomposition atmosphere. Increasing the particle size from 13 to 50 nm by changing the Ag loading from 2 to 15 wt% increased the selectivity from 35 to 80%. However, increasing the 15 wt% Ag particle size from 48 to 184 nm by varying the heat treatment led to a decrease in selectivity from 80 to 50%. Changing the Ag particle size with both strategies also changes the Ag : Al2O3 surface ratio. The ethylene oxide selectivity is actually correlated to the Ag : Al2O3 surface ratio, rather than to the particle size in this size range. This can be explained by its influence on the probability of a formed ethylene oxide molecule to subsequently further react over support surface groups.

Low infrared emissivity epoxy resin/Ag composite coating with outstanding mechanical properties and saltwater resistance

In this study, a low infrared emissivity coating with good mechanical properties and salt water resistance was prepared by the glass rod coating method, using epoxy resin, flake Ag powder, and graphene as a functional pigment, binder, and interface modifier, respectively. The study systematically investigated the impact of Ag powder particle size, as well as the addition of silver powder and graphene, on the coating properties. The larger particle size of the Ag powder led to a significant decrease in emissivity and enhancement of the mechanical properties of the coating. The coating had optimal emissivity and mechanical properties at an Ag particle size of 10 μm. The emissivity and glossiness of the coating can be significantly reduced with the increase in added Ag powder, and the mechanical properties will be significantly improved. The increase in added graphene significantly reduced the glossiness and improved the flexibility of the coating. With a graphene content of 8 wt%, the coating has the best emissivity, glossiness, and mechanical properties at the same time. The epoxy resin/Ag composite coating, modified by graphene, showed good salt water resistance. After being corroded by salt water for 21 days, the emissivity, glossiness, adhesion strength, flexibility, and impact strength of the coating reached 0.535, 14.7, grade 1, 2 mm, and 50 kg · cm, respectively.

Adsorption of toxic methyl iodide over Beta, ZSM-5 and SSZ-13 supported silver adsorbents

The efficient capture of radioactive isotopes of iodine uranium fission reactions is a major issue for safe nuclear energy. To investigate the toxic methyl iodide (CH3I) retention performance of Ag/Beta, Ag/ZSM-5 and Ag/SSZ-13, these Ag zeolites with identical Ag loadings and close Si/Al were prepared. The limited pore volume of ZSM-5 makes a larger size of Ag particles (∼7 nm) than Ag/Beta and Ag/SSZ-13. Silver, in the form of Ag+ ions, enters the cages of the zeolites as Lewis acid sites. In terms of the CH3I retention performance, Ag/Beta rivals the currently reported Ag zeolites applied to capture of radioactive iodine compounds. The CH3I storage capacity of Ag/Beta reaches 1.76 g/gAg. The strong CH3I affinity on Ag/Beta is confirmed by DFT method. The CH3I adsorption energy reaches 121.24 kJ/mol. Kinetics analysis shows that CH3I adsorption on three Ag zeolites observes pseudo-second order model. Good fitting of intra-particle diffusion model on Ag/SSZ-13 also demonstrates that intragranular diffusion is the rate-determining step of CH3I adsorption. The mechanism of CH3I retention is CH3I diffusion within the zeolites and then the formation of AgI species. This work expands the research field of Ag zeolite and contributes to its promising application in the capture of radioactive iodine.

Preparation and Tribological Behavior of Nitrogen-Doped Carbon Nanotube/Ag Nanocomposites as Lubricant Additives

In this study, nitrogen-doped carbon nanotube/Ag nanocomposites (denoted as N-C/Ag) have been synthesized in a urea solution using a hydrothermal method. The carbon nanotubes, AgNO3 solution, urea and poly-dopamine (PDA) served as carbon, silver, nitrogen and carbon sources, respectively. The results show that the diameter of the carbon tubes was about 30 nm, and the Ag nanoparticles, with a diameter of ca. 10 nm, dispersed on the carbon tube surface. The Ag particle size decreased with a lower degree of crystallinity at a high temperature in the presence of urea. The friction and wear behavior of the oil acid (OA) modified N-C/Ag (OAN-C/Ag) as an additive in liquid paraffin (LP) were studied using a four-ball friction and wear tester. The results have shown that the coefficients of friction (COFs) and wear scar diameters (WSDs) of steel balls lubricated with LP-OAN-C/Ag decreased by 27.3% and 25.3%, respectively, relative to pure LP. Tribofilms containing Ag, carbon and nitride were formed on the worn steel ball surfaces. Details, the carbon, Fe2O3, azides and nitride, Ag and alloy and other compounds on the wear scars may improve tribological properties. The synergistic effect of carbon, Ag and urea plays a critical role during sliding.

Size and surface charge of Ag particles influence the horizontal transfer of antibiotic resistance genes via transformation

With the rapid development of nanotechnology, nanomaterials have been prepared with diverse sizes and surface properties. However, the influences of these properties on the horizontal transfer of antibiotic resistance genes (ARGs) are still unclear. Here, two groups of Ag particles were prepared, one group with the same negative charge and different sizes (9, 72 and 1885 nm), the other group with similar sizes (72 and 67 nm) and different charges (−12.7 and +22.6 mV) and their effects on ARGs transformation were investigated. The results revealed that 9 nm Ag at 1000 μg/L induced a 14.56-fold increase in transformation, which was 2.05 and 3.91 times higher than that of 72 nm and 1885 nm Ag particles, respectively. When the size was similar, the positively charged Ag stimulated an 11.59-fold increase in transformation, which is 1.63-fold higher than that of the negatively charged Ag. Investigation of the underlying mechanisms suggested that Ag particles with a smaller size and/or positive charge induced more intercellular reactive oxygen generation and membrane damage than Ag particles with large size and/or negative charge. This study exposed the potential ecological risks of Ag particles with small size and positive charge in accelerating the dissemination of ARGs and highlighted concerns about the management of nanomaterials with varying structural properties.

Comparison of size distributions of recovered particles generated from Ag wire in air by pulsed wire discharge and electric explosion of wire methods

Electric explosion of a wire (EEW) with discharge and pulsed wire discharge (PWD) are essential methods for producing nanosized and micronized metal particles. The study of Ag particle size distributions is important for Ag particle recovery from photovoltaic panel sheets using these methods performed in previous studies. In this study, we examined the size distributions of Ag particles generated from an Ag wire in air by EEW and PWD to clarify the difference between, and effects of these methods on particle generation. The particle size distribution generated in PWD was concentrated in a narrower range. The simulation results suggest that volume expansion occurred for a liquidized Ag wire in EEW and for a gasified Ag wire in PWD. Visualized images of processes and current waveforms in EEW and PWD indicated that after the wire explosion the restrike with plasma occurred in the expanding Ag particles in air in PWD. These results suggest that the narrower particle size distribution obtained in PWD may be attributable to monodisperse powderization by plasma evaporation of the gasified wire. These results show that PWD with plasma of an Ag wire in air effectively creates particles that are more monodispersed than those formed by EEW.

Enhanced mechanical and electrical performance of Ag-4wt%ZrB2 contact materials prepared with different-sized Ag powder

Ag-ZrB2 composite is a promising candidate used as electrical contact materials. So far, the effect of Ag particle size on the microstructure, properties and arc erosion behavior of Ag-based contact materials is unclear. In this work, the Ag-4 wt%ZrB2 contact materials were prepared with coarse and fine Ag powder utilizing wet mixing and spark plasma sintering. The microstructures and eroded morphologies of the Ag-4 wt%ZrB2 contact materials were characterized, the arc duration/energy, welding force and mass loss were investigated, and the effect of Ag particle size on arc erosion behavior was discussed as well. The results show that the fine Ag powder is beneficial for the uniform dispersion of the ZrB2 in the Ag matrix, and enhancement on the hardness and electrical conductivity. As compared to the Ag-4 wt%ZrB2 contact material prepared with the coarse Ag powder, the hardness and electrical conductivity of the Ag-4 wt%ZrB2 contact material prepared with the fine Ag powder are increased by 66.26% and 32.92%, respectively. Furthermore, the contact material prepared with fine Ag powder has a shorter break-arc duration and lower break-arc energy, as well as a smaller welding force and less mass loss, thereby exhibiting superior arc erosion and welding resistance.

Improved quality and inhibited aggregation of Ag–In alloy films

Ag atoms agglomeration at environmental conditions limits its applications. Here, the influences of indium addition on the microstructure and performance of Ag films were investigated. The results show that the particle size, pore size, and roughness of Ag–In alloy films are greatly reduced compared with those of the Ag film. A small amount of indium can efficiently inhibit the agglomeration/migration of Ag atoms and thus significantly improve the reflective performance at damp heat environment. These results show that alloying is an effective method to inhibit Ag atoms migration/agglomeration at environmental conditions.

Gamma Radiation Synthesis of Ag/P25 Nanocomposites for Efficient Photocatalytic Degradation of Organic Contaminant.

Titanium dioxide (TiO2) has garnered significant attention among various photocatalysts, whereas its photocatalytic activity is limited by its wide bandgap and inefficient charge separation, making the exploration of new strategies to improve its photocatalytic performance increasingly important. Here, we report the synthesis of Ag/P25 nanocomposites through a one-step gamma-ray radiation method using AgNO3 and commercial TiO2 (Degussa P25). The resulting products were characterized by powder X-ray diffraction, UV-Vis diffused reflectance spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of free radical scavengers, feed ratios of Ag/P25, and dose rates on the photocatalytic activity of the Ag/P25 nanocomposites were systematically investigated using rhodamine B under Xenon light irradiation. The results showed that the Ag/P25 photocatalyst synthesized with a feed ratio of 2.5 wt% and isopropyl alcohol as the free radical scavenger at a dose rate of 130 Gy/min exhibited outstanding photocatalytic activity, with a reaction rate constant of 0.0674 min-1, much higher than that of P25. Additionally, we found that the particle size of Ag could be effectively controlled by changing the dose rate, and the Ag/P25 nanocomposites doped with smaller size of Ag nanoparticles performed higher photocatalytic activities. The synthesis strategy presented in this study offers new insight into the future development of highly efficient photocatalysts using radiation techniques.