Growth Of Silver Particles Research Articles

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.

NMP limits silver particle size to solve deposited film breakup problems

Metal based electroreflective devices (MERDs) have gained wide attention in recent years in the fields of smart windows and automotive glass due to their excellent photo-thermal modulation capability in the visible and near-infrared wavelength bands due to their high reflectivity. However, the high porosity due to the island-like growth of silver particles makes the devices susceptible to electrodeposited film breakage during prolonged energization or bleaching. This will seriously affect the effectiveness and stability of the device. In this paper, it is shown that the problem of Ag electrodeposition film fragmentation can be effectively overcome by replacing dimethyl sulfoxide solvent by N-methylpyrrolidone (NMP). The optical constants during film deposition were tested by the spectroscopic ellipsometry technique, and the porosity was calculated (reduced by 21.6%). The results show that MERDs with NMP as the solvent have more and more dispersed silver deposition sites, which leads to lower porosity of the silver deposited film during the deposition process. In addition, the lower turn-on voltage, greater contrast, longer memory effect, and greater coloring efficiency reveal that they are more promising for energy-saving applications.

Impact of polymeric stabilizers on the transformation and sustainable recovery of silver microstructures from spent button batteries

This paper presents a simple, rapid, highly efficient, and environmentally friendly technique for recovering silver microstructures from spent button batteries. The technique exploits the reducing ability of H2O2 to convert silver sources into high-purity silver at the microscopic scale. The influence of polymeric stabilizers (PVP and PVA) on the formation of silver microstructures was elucidated. The results revealed that polymeric stabilizers play a crucial role in controlling the growth of silver particles at the microscopic level. Specifically, PVP affords a homogeneous silver microplate, whereas PVA facilitates the formation of isotropic spherical microparticles. Additionally, the effect of the molecular weight (Mw) of the stabilizers on the silver particles was examined. The Mw of PVP significantly impacts its anti-aggregation properties. Similarly, the Mw of PVA affects the formation of silver microstructures. The high purity of the recovered silver microstructures was verified by EDX and XRD. Finally, the optimal recovery conditions involving 360,000 and 150,000 g/mol for PVP and PVA, respectively with 0.5 % w/v) were implemented to recover silver from button batteries. These battery residues were successfully transformed into highly pure silver microplates and microspheres using those respective polymeric stabilizers. The developed synthesis approach will facilitate the sustainable recovery of silver from spent button batteries, addressing the environmental, and resource challenges associated with battery waste.

Preparation of Graphene Nanosilver Composites for 3D Printing Technology

At present, graphene in two-dimensional carbon nanomaterials is a material with excellent properties. Its preparation technology and application prospects are very wide. The most common one is the chemical redox method, which can make graphite into graphite oxide dispersed in water. Graphene oxide obtained by the Hummers method has a wrinkled structure. In order to broaden the application field of graphene and give full play to its excellent properties, the current research on graphene mainly focuses on the preparation and application of functional composite materials as a matrix material or reinforcement material. Due to its special two-dimensional structure, it has a large specific surface area, good biocompatibility, and stable physical and chemical properties, making it an excellent nanoparticle carrier. The graphene-supported silver nanoparticles can effectively prevent the aggregation and stacking between particles, improve the electrochemical performance of the composite material, and expand its application range. In this article, the assisted preparation of graphene nanosilver composites by 3D printing technology (three-dimensional printing) was studied. 3D printing technology is a rapid prototyping technology that emerged in the 1980s. 3D printing technology is based on discrete stacking and realizes rapid processing of models by directly outputting data from the printing device. In this article, a new type of graphene oxide (GO) was prepared by the modified Hummers method. In the case of NaOH aqueous solution as a catalyst, silver nitrate and GO were used as precursors, and XRD, infrared spectrum, Raman spectrum, and other methods were used. The crystal structure and morphology of Ag/rGO under different conditions were studied, thus revealing the growth of silver particles and the changes of oxidized functional groups under different conditions. It was found that the intensity of the two peaks in the GNs-Ag-2 Raman spectral curve was seven times that of the GNs peak.

Influence of atmosphere, interparticle distance and support on the stability of silver on α-alumina for ethylene epoxidation

The stability of supported metal particles is an important parameter in heterogenous catalysis. For silver catalysts supported on α-alumina, industrially used in ethylene epoxidation, the loss of silver surface area as result of particle growth is one of the most important deactivation mechanisms. In this work, the growth of silver particles was investigated by exposing catalysts to thermal treatments. The presence of oxygen during heating strongly enhanced particle growth, and the interparticle distance was a crucial parameter. However, restricting movement of complete silver particles using cage-like α-alumina did not limit particle growth. These findings indicate that Ostwald ripening was the dominant mechanism behind particle growth, with the diffusion of oxidized silver species being a rate limiting factor. Finally, higher surface area α-alumina provided better silver stability during ethylene epoxidation, with only limited decrease in selectivity. This makes silver supported on high surface area α-alumina promising candidates for ethylene epoxidation catalysis.

The role of metal–support interaction in Ag/CeO2 catalysts for CO and soot oxidation

Ag/CeO2 catalysts with a silver loading of 10 wt.% have been prepared by three different techniques: impregnation, Ag/CeO2 (imp), impregnation of prereduced CeO2, Ag/CeO2 (red-imp), and co-deposition precipitation, Ag-CeO2 (co-DP). The features of the prepared composites have been studied by low-temperature N2 sorption, TGA, XRF, TPR-H2, TEM HR, XPS and Raman spectroscopy. The Raman and XPS results show that the addition of silver to CeO2 significantly increases the defectiveness of CeO2 particles, and such an effect is a function of the preparation method. The Ag-CeO2 (co-DP) and Ag/CeO2 (red-imp) catalysts show enhanced interfacial Ag–CeO2 interaction caused by the epitaxial growth of silver particles (d111 = 2.35 Å) on the CeO2 surface (d111 = 3.1 Å) as well as high amount of oxygen vacancies. A morphology-dependent interplay between the oxygen vacancies and the strength of the Ag–CeO2 interaction has been revealed. Strengthening of the metal–support interaction enhances the catalytic activity of the composites in both CO oxidation and soot combustion.

Effects of amine types on the properties of silver oxalate ink and the associated film morphology

Silver conductive ink using silver oxalate as silver precursor has attracted considerable research interest due to its unique properties. However, silver oxalate has poor dissolvability in organic solvents and high thermal decomposition temperature, the latter is not desirable for pattern formation on some low cost polymer based flexible substrates. In this paper, different kinds of alkylamine were chosen as ligands to formulate silver oxalate inks to address the mentioned issues. The role of amines in silver oxalate based inks was studied in detail. The influence of amine types on thermal property, stability and electrical performance of the formulated silver oxalate inks was investigated. The relationships between them were established and elucidated. The results show that highly conductive silver films with controlled microstructure features can be achieved for low temperature sintering by selection of an appropriate amine as the latter has a strong influence on the decomposition temperature of the formed silver–amine complex and it determines the nucleation and growth of silver particles in the film formation process. The chemical reactions occurring within the ink were also studied. An optimal silver complex ink was prepared by using blended amines as ligands finally, producing a uniform silver film with good quality and favorable conductivity at 150 °C. The results are important for future design of stable and high conductive silver complex inks for practical applications.

Ultrasonic Characterization of Silver Nano Fluid

Nano fluids are stable suspensions of nano particles in a liquid. Metal oxide nanoparticles offer great merits over controlling rheological, thermal, chemical and physical properties of solutions. The effectiveness of a nanoparticle to modify the properties of a fluid depends on its diffusive properties with respect to the fluid. An important application of Nano fluids containing nano particles is as a coolant, since the addition of only a few volume percent of nano particles to a liquid coolant and significantly improves its thermal conductivity. A heat exchange device using nanofluid needs to operate at best nanoparticle loading to get the maximum heat transfer performance. Due to its antimicrobial properties, the future therapeutic directions may include nano-silver as an anti-inflammatory and as anti-platelet agents and antiviral drugs. Owing to the applications of nano silver particles, attempts has been made in the present study to synthesis silver nano particles and characterized with the help of ultrasonic technique. Different acoustic properties of AgNO3 nanofluids are studied with the help of Ultrasonic technique. Silver nanofluids are synthesized by chemical reduction method. The chemical reduction method involves the reduction of AgNO3 in aqueous solution by a reducing agent in the presence of a suitable stabilizer, which is necessary in protecting the growth of silver particles from aggregation. Ultrasonic velocity and density values are measured for different concentrations of AgNO3 nanofluids. The acoustic parameters like adiabatic compressibility, intermolecular free length, and acoustic impedance are calculated from the experimental data. The variation of ultrasonic velocity and other parameters with particle concentration are discussed on the basis of interaction of ultrasonic wave with the nano sized silver particles.

Control of the Size of Silver Nanoparticles and Release of Silver in Heat Treated SiO₂-Ag Composite Powders.

The growth of silver nanoparticles, the activation energy for silver particle growth, and the release of silver species in heat treated -Ag composite powders are investigated. The silver particle growth is controlled by heat treatment for 75 min of the as-synthesized -Ag composite powder at 300–800 °C. During heat treatment the mean size of the Ag particles increases from 10 nm up to 61 nm with increasing temperature, however, the particle size distribution widens and the mean size increases with increasing heat treatment temperature. Based on X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) studies, silver particles are crystalline and in a metallic state after annealing in all -Ag composite powders. The growth of Ag particles is suggested to take place via diffusion and Ostwald ripening. The activation energy for particle growth was determined as 0.14 eV. The dissolution of silver in aqueous solutions from the -Ag composites heat treated, at 300 °C, 600 °C, and 700 °C, was investigated by varying pH and temperature. The dissolution was reduced in all conditions with increasing silver particle size, i.e., when the total surface area of Ag particles is reduced. It is suggested that the dissolution of silver from the composite powders can conveniently be adjusted by controlling the Ag particle size by the heat treatment of the composite powder.

Fluorescent Ag+-exchanged zeolite nanoparticles with improved photoluminescence properties via X-ray irradiation

Fluorescent Faujasite (FAU)-Y Ag+-exchanged zeolite is a lanthanide-free phosphor with a high photoluminescence (PL) quantum yield to convert near-ultraviolet (near-UV) to visible light. Here, we focused on nanometer-sized fluorescent FAU Ag+-exchanged zeolite as a wavelength converter for optoelectronic devices. The prepared Ag+-exchanged zeolite nanoparticles were irradiated with X-rays to improve their PL properties because X-ray irradiation does not possess the disadvantages of other treatments, such as aggregation and sintering of nanoparticles exposed to thermal treatment, excessive growth of silver particles with visible light absorption following chemical reduction, and amorphization of zeolite by high-energy electron beam irradiation. FAU-Y zeolite nanoparticles were prepared by template-free hydrothermal synthesis and then fluorescent Ag+-exchanged zeolite nanoparticles were obtained through the ion exchange of Na+ with Ag+. The prepared Ag+-exchanged zeolite nanoparticles were irradiated by X-rays from a commercial tabletop device. The average size of the as-prepared zeolite nanoparticles was 35.7 ± 12.6nm according to transmission electron microscopy (TEM) images. TEM also confirmed that Ag-related particles such as silver clusters and/or silver nanoparticles were generated and grew from Ag+, possibly through reduction accompanied with oxidation of oxide ions of the zeolite framework during X-ray irradiation. PL quantum efficiency was enhanced by X-ray irradiation by up to ~3 times. Analysis of PL properties and electron spin resonance spectra implied that fluorescent Ag42+ clusters were formed under X-ray irradiation, resulting in the enhancement of PL quantum efficiencies. Similar behavior was also observed for micrometer-sized Ag+-exchanged zeolites. X-ray irradiation of fluorescent Ag+-exchanged zeolites is therefore a useful method to improve their PL properties.

A study on the CNTs-Ag composites prepared based on spark plasma sintering and improved electroless plating assisted by ultrasonic spray atomization

Carbon nanotubes reinforced silver composites (CNTs-Ag composites) are considered as a promising candidate for high-performance contact materials with the potential properties of low contact resistance, high thermal conductivity and excellent mechanical performance. While at present the dispersion of CNTs in silver matrix and the interfacial bonding of the composites remain problems to be resolved or enhanced. In this study, silver nanoparticles coated carbon nanotubes (Ag@CNTs) were synthesized through an improved electroless plating method assisted by ultrasonic spray atomization, which inhibited excessive growth of silver particles and led to much more uniform nanometer grain-sized coating. The Ag@CNTs were solution ball-milled (SBM) with Ag powders and then were densified by spark plasma sintering (SPS). The composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). The results showed the CNTs dispersion in Ag matrix was improved benefitting from the homogeneous Ag nanoparticles distribution on CNTs, and correspondingly, the hardness and electrical conductivity were significantly improved. The mechanism may result from the combination of more homogeneous CNTs dispersion and tighter interface bonding in composite materials.

Electrochemical Observation of the Plasmonic Effect in Photochromic Ag Nanoparticle Filled Mesoporous TiO2 Films

We report photoelectrochemical measurements from mesoporous titanium dioxide filled with silver nanoparticles under illumination. A 200 mV potential switch of silver ion reduction is observed, depending on light wavelength. An easier reduction of silver in the presence of light is linked to plasmon induced charge separation (PICS). SEM and TEM analysis before and after photoelectrochemistry have also shown an electrochemical Ostwald ripening during continuous visible irradiation, with a growth of silver particles at the sample surface. The combined use of mesoporous structures and electrochemical characterization enabled the change in silver reactivity during PICS to be quantified and emphasizes the role of plasmon in photochromism.

Improved electroless plating method through ultrasonic spray atomization for depositing silver nanoparticles on multi-walled carbon nanotubes

A novel method was developed to deposit nanosized silver particles on multi-walled carbon nanotubes (MWCNTs). The electroless plating of silver on MWCNTs accomplished in small solution drops generated by ultrasonic spray atomization, which inhibited excessive growth of silver particles and led to much more uniform nanometer grain-sized coatings. The results showed that pretreatment was essential for silver particles to deposit on the MWCNTs, and the electrolyte concentration and reaction temperature were important parameters which had a great influence on the morphology and structure of the silver coatings. Possible mechanisms of this method are also discussed in the paper.

An investigation of nanometal-glass hybrid nanocomposites produced by ion exchange and annealing process

Nanometal-glass hybrid nanocomposites are formed by the ion exchange technique of dipping the host matrix glass in the molten salt bath. This study aims to investigate Ag-ion exchanged and annealed soda-lime silicate glasses in terms of their optical and structural properties. The effects of experimental conditions (composition of the salt bath, temperature and time of ion exchange and annealing process, the atmosphere of annealing) on the plasmonic and optical behavior were examined. The produced nanometal-glass hybrid nanocomposites were characterized by UV-Vis-NIR, HRTEM-EDS, SEM, XRD, and AFM to determine nanoparticle size, shape, structure, silver particle growth, and glass surface topography.

Engineering the surface functionality of 45S5 bioactive glass-based scaffolds by the heterogeneous nucleation and growth of silver particles

An emerging topic in the field of biomaterials is the incorporation of silver ions, metallic silver or silver oxides into bioactive glasses to impart novel functionalities. In this work, a new approach of surface functionalization of 45S5 bioactive glass (BG) is introduced. In contrast to more common methods, which are based on the inclusion of silver during the sol–gel synthesis of BG, our method allows the surface functionalization of BG powders and BG scaffolds after their preparation. Hereby, we demonstrate the transferability of a previously reported approach on the wet chemical synthesis of cup-like and dendritic silver patches first from colloidal silica particles to BG particles and further to macroscopic highly porous BG scaffolds which were prepared by the sacrificial foam replica technique. The time-dependent silver releases of BG scaffolds with different silver loadings into simulated body fluid (SBF) were measured. Further studies were addressed to investigate the bioactivity of BG scaffolds before and after the silver coating procedure. It was found the silver deposition on 3D BG scaffolds did not affect the formation of crystalline hydroxyapatite during immersion into simulated body fluid.

Temperature-Dependent Dwell-Fatigue Behavior of Nanosilver Sintered Lap Shear Joint

A series of dwell-fatigue tests were conducted on nanosilver sintered lap shear joint at elevated temperatures from 125 °C to 325 °C. The effects of temperature and loading conditions on dwell-fatigue behavior of nanosilver sintered lap shear joint were systematically studied. With higher temperature and longer dwell time, creep played a more important part in dwell-fatigue tests. Creep strain accumulated during maximum shear stress hold was found partly recovered by the subsequent cyclic unloading. Both the fracture mode and silver particle growth pattern were characterized by X-ray tomography system and scanning electron microscope (SEM). The mean shear strain rate γ˙m synthesized the effects of various factors, such as temperature, shear stress amplitude, mean shear stress, and dwell time, by which the fatigue and dwell-fatigue life of nanosilver sintered lap shear joint could be well predicted within a factor of two.

Nanoparticle Shape Evolution and Proximity Effects During Tip-Induced Electrochemical Processes.

Voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When the grid spacing is small compared with the size of the formed Ag particles, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag(+)/Ag redox reaction to Ag(+)-ion diffusion with the increase in the applied voltage and pulse duration. This study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.

Selective growth of silver particles on the facets of synthetic diamond

We have shown for the first time that simple annealing of silver–synthetic diamond mixtures in air or oxygen at 600–700 °C leads to selective growth of silver particles on the {100} facets of diamond, while no growth is observed on the {111} facets. Annealing at a temperature higher than 750 °C results in significant morphological changes in the heterostructure: silver particles grow not only on the cube but also on the octahedral facets.

Multifunctional silver film with superhydrophobic and antibacterial properties

Material properties are strongly dependent on material structure. The large diversity and complexity of material structures provide significant opportunities to improve the properties of the materials, expanding their applications. Here, we discuss the fabrication of a multifunctional silver film prepared by controlling the nucleation and growth of silver particles. Silver films with high hydrophobicity and antibacterial activity were fabricated by adopting an electrochemical approach. The dependence of the hydrophobic and antibacterial properties on the size and shape of the silver particles was first investigated. Small-sized silver particles exhibited a high antibacterial rate, while a porous silver film composed of dendritic particles showed a significant hydrophobic activity. By regulating the reaction time, current density, and silver salt concentration, a silver film with a contact angle of 150.9° and an antibacterial rate of 54.7% was synthesized. This study demonstrates that finding a compromise between different material structures is a suitable way to fabricate multifunctional devices.

Transition Metal Ion-induced Anisotropic Architectures Using 4,4’-dicarboxy-2,2’-bipyridyl-silver Nanopetals

Designing anisotropic nano- and micro-structures are imperative in many technology oriented fields. Here we have reported a self templating method, where flower like microstructure of silver particles were used as template to generate several anisotropic structures such as rectangular cum dumbbell, cubes, hexagonal whiskers, and rectangular bars etc. under controlled catalytic activity of Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ respectively. The initial flower like microstructure (template) of silver particles have been prepared from silver salt using disodium salt of 4,4’-dicarboxy-2,2’-bipyridyl(Na2dcbpy) as the reducing as well as capping agent. Then this architecture was used as the initial template to generate several anisotropic structures. The straightforward anisotropic microstructure preparation procedure does not require any other external template, which avoids the subsequent complicated workup. The nucleation processes and optical properties were studied using optical absorption spectroscopy. The anisotropic structure of the as-synthesized Ag particles and the formations of various shaped microstructures have been confirmed by Scanning Electron Microscopy (SEM). A possible mechanism has been proposed explaining the role of dcbpy in the growth of silver particles and the transition metal ion induced anisotropic structures.