Silver Nanopowder Research Articles

Preparation and Antibacterial Effect of Nanopalygorskite Supported Nano-Silver Powder

A novel method was used to make palygorskite supported nano-silver powder at room temperature. XRD result showed the presence of silver in the final product. TEM investigation revealed that nano-sliver particles of 6-10 nm in diameter were successfully attached on surface of palygorskite fiber. FTIR was also used to clarify the formation mechanism of our method. The antibacterial effect of palygorskite supported nano-silver powder was investigated. Palygorskite supported nano-silver powder had good antibacterial activity on standard Escherichia coli and Staphylococcus aureus.

Solvent effects on arc discharge fabrication of durable silver nanopowder and its application as a recyclable catalyst for elimination of toxic p-nitrophenol

Abstract Various types of nanosilver have been synthesized by a variety of methods, among them “arc discharge” stands with numerous advantages and calls for a much higher attention. Here, an unprecedented durable powder form of silver nanopowder (AgNP) is produced by DC arc discharge through a simple, convenient, and economical route, at a current of 5–10 A/cm2. Effects of media are probed against the quality of the resulting nanoparticles. Among eleven media explored, glycerin/water (10% w/w) is found to afford the highest yield, purity, and relatively smaller size of AgNP with the desired morphology. To our joy, the as-prepared-AgNP proves efficient in catalytic green reduction of p-nitrophenol (PNP) which is one of the most potent water pollutants. Our reduction of PNP by NaBH4 in the presence of AgNP in water is monitored by UV–Vis spectrophotometry. A provisional mechanism is proposed for this reaction which appears fast and completes in two minutes. The AgNP is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hence, arc discharge fabrication of durable AgNP is maximized by adapting glycerin/water as the medium of choice; and the resulting AgNP catalyzes toxic PNP conversion into p-aminophenol.

Synthesis of silver nanoparticles by silver salt reduction and its characterization

The wet chemical method route by metal salt reduction has been used to synthesize nanoparticles, using silver nitrate as an inorganic salt, aldehyde as a reducing agent and amino acid as a catalyst. During the reaction aldehyde oxidizes to carboxylic acid and encapsulates the silver nanoparticles to prevent agglomeration and provide barrier in the growth of particle. The existing work produces particles using lab grade chemical, here the presented work is by using industrial grade chemicals to make the process more cost & time effective. The nano silver powder has been studied for their formation, particle size, shape & compositional analysis using Scanning Electron Microscope (SEM) equipped with EDS. The particles size distributions were analyzed by Laser Particle Analyzer (LPA), structure & morphological analysis using x-ray diffraction (XRD) and Fourier-transform-infrared Spectroscopy (FTIR) confirmed the stabilization of particles by coating of carboxylic group. These studies infer that the particles are mostly spherical in shape and have an average size between 70 to 350 nm.

Low Temperature Consolidation of Micro/Nanosilver Die-Attach Preforms

Organically passivated silver nanopowder paste-based sintering is considered a promising solution for die-attach in high temperature power and sensing electronic devices. However, oxygen requirements during burnout and inherently high shrinkage rates limit their use to small die sizes. This work reports an alternative fabrication method that resolves decomposition and shrinkage issues of the die-attach by utilizing a prestressed optimized tape cast mixture of micro- and nanosilver particles with a polypropylene carbonate binder. The effects of prestressing, micro/nanosilver bimodal distribution, and polymer content on resulting microstructure and shear strength were investigated. Prior to application as a die-attach, uniaxial compression of the tape was found to significantly decrease shrinkage and improve green strength. This pre-stressing strategy allows for a decoupling of the resulting die-attach materials properties from the pressure applied during assembly. Bimodal mixtures consisting of 1–3 μm spherical powders with nanosilver resulted in shear strengths comparable to those of pure nanosilver. Shear strength decreased as bimodal particle size increased above 5 μm. A polymer content of ∼10 wt.% polypropylene carbonate combined with prestressing was identified as optimal for maximizing die-attach shear strength while still maintaining pliability and formability. Tape casts that were prestressed to 212 MPa by uniaxially compression and formulated with 10 wt.% of polypropylene carbonate resulted in a die-attach material with a shear strength of 54 MPa when sintered. These materials were used to demonstrate void-free 25-mm2 die-attach assemblies, suggesting that tape cast micro/nanosilver materials may be a promising die-attach method for high temperature and large-area electronics devices.

Preparation of silver nanostructures from a new benzopyrazine silver(I) nitrate coordination polymer

A new two-dimensional silver(I) coordination polymer, [Ag(Quinoxaline)(NO3)]n (1); Quinoxaline=Benzopyrazine, has been synthesized and characterized by IR and 1H NMR spectroscopy. Silver nanorods were synthesized by calcination of compound 1 at 600°C under air atmosphere. Also, silver nanopowders and silver spongy nanostructures were synthesized by calcination at 400 and 500°C and sol–gel methods. The silver nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and energy-dispersive X-ray (EDAX). The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA).

Investigation on the Morphology of Sintered Silver Nanomaterial for Electronic Packaging Application

Silver nanoparticles are seen as a possible replacement for high temperature solders containing 90-95 wt.% Pb, which is widely used in various applications e.g. automotives. These high temperature solders have been exempted from the Restriction of Hazardous Substances (RoHS) Directive due to very limited drop-in replacement for the high temperature solders. Although the effect of sintering temperature of silver nanoparticles has been studied, the mechanism involved in the changes in the morphology of the particles and interfacial reaction with the substrate as a function of sintering temperature must be understood. In this study the effect of sintering temperature on the morpohology of Ag nanoparticles is discussed. The Scanning Electron Microscopy (SEM) analysis was used to analyze the changes in morphology of silver particles agglomerates with sintering temperatures. Results showed necking of the nanosilver powder, which indicated the occurrence of sintering through grain boundary diffusion process. Meanwhile, the micro-silver powder showed agglomeration of particles but no necking was observed. The study has shown that the Ag agglomerates was observed to undergo various changes to the particle morphology with different sintering temperatures.

Bifunctional electrocatalyst for oxygen/air electrodes

Nano-Silver powder has been studied as bi-functional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. Ag nano-powder has been prepared by a simple wet chemical method with Silver nitrate as precursor and Glucose as reducing agent. X-ray Diffraction and Scanning Electron Microscopy studies were carried out to characterize the Silver catalyst. Electrochemical oxygen evolution characterization shows anodic peak typically at the range between 0.350 and 0.514V Vs Hg/HgO corresponding to Silver oxidation followed by the onset of oxygen evolution at 0.706V. Oxygen reduction reaction studies carried out using Rotating Disc Electrode (RDE) confirm the four electron reaction mechanism. Ag catalyst shows promising characteristics for oxygen evolution and oxygen reduction.

Tuning the thermal diffusivity of silver based nanofluids by controlling nanoparticle aggregation

With the aim of preparing stable nanofluids for heat exchange applications and to study the effect of surfactant on the aggregation of nanoparticles and thermal diffusivity, stable silver colloids were synthesized in water by a green method, reducing AgNO3 with fructose in the presence of poly-vinylpyrollidone (PVP) of various molecular weights. A silver nanopowder was precipitated from the colloids and re-dispersed at 4 vol% in deionized water. The Ag colloids were characterized by UV–visible spectroscopy, combined dynamic light scattering and ζ-potential measurements, and laser flash thermal diffusivity. The Ag nanopowders were characterized by scanning electron microscopy and thermal gravimetric analysis. It was found that the molecular weight of PVP strongly affects the ζ-potential and the aggregation of nanoparticles, thereby affecting the thermal diffusivity of the obtained colloids. In particular, it was observed that on increasing the molecular weight of PVP the absolute value of the ζ-potential is reduced, leading to increased aggregation of nanoparticles. A clear relation was identified between thermal diffusivity and aggregation, showing higher thermal diffusivity for nanofluids having higher aggregation. A maximum improvement of thermal diffusivity by about 12% was found for nanofluids prepared with PVP having higher molecular weight.

Metallic Silver from Leach Liquor: A New Approach for Silver Nano Metal Synthesis

The leach liquor of a low grade silver ore containing 0.5% Ag is used to produce two varieties of metallic silver following two routes. Route-I leading to silver mould by precipitating out silver chloride with 1.62g/L NaCl and later on roasting the silver chloride with Na2CO3 in 2:1 ratio at 1000°C for 2h. Route-II leading to silver nano metals by treating the leach liquor with 5% (v/v) hydrazine hydrate as reductant and 10mL of 0.01M sodium lauryl sulfate in 100mL of leach liquor as surfactant. The paper first time reports the production of silver nano metal from impure leach liquor. This is a new dimension to the conventional nano metal preparation. Silver is obtained in nature in its native form. Apart from coin making (ancient eras) and jeweler making, silver has its uses in various fields like electrical, thermal and pharmaceuticals due to its high electrical and thermal conductance’s and for its proficient antibacterial activity respectively. Extraction of silver deals with the leaching with different reagents like ferricyanide,1-3 cyanide,4-5 thiosulfate,6-8 thiourea,9-11 ferric ion,12 sulfate,13 nitric acid14-15 and chloride/hypochlorite.16 Ultrasound assisted leachings17-18 are also one of the recent trends. Silver is extracted from the leach liquor through electrochemical deposition, 19 electroseparation20 and precipitation.21 Synthesis of silver nano metal is one of the most upto-date investigations in today’s world due to its high applicability. Nano metals show amazing properties due to high surface to volume ratio. Nano clusters provide a potential platform to study atoms as well as bulk and looking towards both the sides being in the middle.22 Nano metallic particles have many such unique properties as compared to the bulk. Investigations so far have reported the preparation of silver nano particle synthetically from silver nitrate,23-26 silver diamine27-28 and silver thiosulfate.23 One thing to be noted here that all those silver nano particles are produced from high grade pure salts. This paper first time reports the preparation of metallic silver from a leach liquor of low grade silver ore containing 0.5% silver which would never be used for industrial silver production. Nano metal synthesis from a pure salt is in ease due to its purity and assurance of the absence of other ions. But synthesizing pure metal nano particles from a solution having varieties of ions is a challenging task. The advantages of producing silver nano metal from impure leach liquor are 1) it may suggest another method of metal extraction from the leach liquor apart from the conventional ones, 2) it would give a process to produce nano silver from leach liquor of various kind of silver ores and the secondary silver materials and 3) it will substitute the electrode position and electro separation thereby reducing the electrical energy. Moreover this paper also reports the production of metallic silver mould from route-I via precipitation of silver chloride followed by roasting and metallic silver nano powder via reduction method. (Chemical bonds between primary particles) state, since their

Preparation of Highly Stabilized Silver Nanopowders by the Thermal Reduction and Their Properties

Silver nanopowders were prepared from silver 2-ethylhexylcarbamate (Ag-EHCB) complexes by simple thermal reduction at <TEX>$85^{\circ}C$</TEX> without any reducing agent in organic solvent. 2-Ethylhexylammonium 2-ethylhexylcarbamate (EHAEHC) was investigated in terms of their abilities to stabilize the silver nanoparticles (Ag-NPs) and its subsequent effects on the preventing aggregation between Ag-NPs. Conditions (concentration of stabilizer and reaction time) used to reduce Ag-EHCB complex were systematically varied to determine their effects on the sizes of Ag-NPs. The formation of the stabilized Ag-NPs were easily monitored by UV-vis spectroscopy and characterized by TGA, TEM, SEM and XRD. When EHAEHC was used as a stabilizer, Ag-NPs of 10-30 nm in diameter were easily obtained in high yield. Silver patterns were obtained from a silver nano-paste by heat treatment at <TEX>$200^{\circ}C$</TEX> in air and were found to have resistivity values of <TEX>$2.9{\times}10^{-8}\;{\Omega}{\cdot}m$</TEX>.

Effects of capping agents on the dispersion of silver nanoparticles

This study investigated and compared the dispersion properties of two silver (Ag) nanopowders synthesized by using oleic acid (OA) and poly(acrylic acid) (PAA) as surface capping agents. The experimental results for the zeta potential and sedimentation measurements when using the OA-capped Ag nanopowder, denoted as Ag@OA, showed that both dispersants, poly(ethylene imine) (PEI) and PAA, were efficient at improving the dispersion stability of the Ag@OA in water. The anionic dispersant PAA was efficient at improving the dispersion of the PAA-capped Ag nanopowder, denoted as Ag@PAA, while the cationic dispersant PEI failed completely, a result attributed to polymer bridging between the dispersant (PEI) and the capping agent (PAA). Nevertheless, the particle agglomeration caused by the polymer bridging mechanism did not occur in the dispersion system of the PEI-dispersed Ag@OA.

Effects of the Ratio of Surface Protective Agent on the Preparation of Nano-Silver

It has many advantages with liquid phase reduction method to prepare the nano-silver, such as experimental conditions are simple, low cost, energy-saving, etc.. At the same time, the nano silver powder prepared by this method has high surface activity, catalytic property and wide usage. In this paper, nano-silver powder was prepared by changing the amount of protective agents with chemical liquid phase reduction method. This paper focuses on the impact of the amount of protective agent on the nano-silver. In addition, we also analyzed the reaction temperature, PH value of solution, viscosity and electrical conductivity on the preparation of nano-silver. Finally, test results from the TEM shows that the nano-silver was prepared with smaller size, uniform size and good dispersion.

SAC 305 solder paste with carbon nanotubes – part I: investigation of the influence of the carbon nanotubes on the SAC solder paste properties

PurposeThe purpose of this paper is to study the manufacturing of SAC 305 solder paste with multiwall carbon nanotubes (MWCNT) before and after structure modification and also to investigate the added carbon nanotubes' influence on the technological properties and the microstructure of “nano” solder pastes. This work is a continuation of similar previous studies of SAC solder pastes with silver nanopowder additions.Design/methodology/approachThe authors applied functionalization and esterification methods for the structural modification of the carbon nanotubes. The “nano” solder paste preparation was performed with the use of a two‐stage method of carbon nanotube dispersion in “own‐manufactured” SAC 305 solder paste. To determine the technological properties of the “nano” solder paste, slump, solder ball, wetting and spreading tests were applied according to the existing standards. Standard metallographic procedures were applied for microstructural analysis.FindingsAs expected on the basis of the previous studies of SAC solder pastes with silver nanopowders, positive results were obtained for the own‐manufactured SAC 305 solder paste with carbon nanotubes by applying the dispersion method. Also applied were functionalization and esterification methods, whose results showed microstructural changes in the carbon nanotubes. The “nano” SAC solder pastes showed a positive influence on the slump properties, compared to the basic SAC solder paste. The authors proved a negative influence of the carbon nanotubes' addition (dependent on their concentration) on the spreading and wetting of the SAC solder paste on a copper substrate, which provoked the non‐wetting and dewetting phenomena. A slight improvement was observed for the “nano” SAC solder pastes with modified carbon nanotubes. The carbon nanotubes' presence in the solder paste showed a positive effect on the growth reduction of the IMCs' thickness, which depended on the type.Research limitations/implicationsThe authors intend to verify the reinforcement effect of the alloys with carbon nanotubes suggested in the literature (the aim of Part II). For this purpose, an assembly process with RC electronic elements on PCBs with Ni/Au and SAC (HASL) finishes will be performed, with the use of the SAC 305 solder paste with modified carbon nanotubes, for the purpose of reflow soldering. Next, measurements of the mechanical strength of the solder joints and their microstructures will be conducted.Practical implicationsIt is suggested that further studies of the mechanical properties and the reliability of solder joints are necessary for the practical implementation of the “nano” SAC solder pastes, but taking into account the wetting data, the investigation should be performed only for “nano” pastes with the lowest additions of modified carbon nanotubes.Originality/valueThe paper demonstrates a method of “nano” solder paste preparation by means of a two‐stage dispersion of carbon nanotubes in the own‐manufactured SAC 305 solder paste and a comparison study of the properties of “nano” pastes with the basic SAC solder paste.

A new radiolabeling method for commercial Ag0 nanopowder with 110mAg for sensitive nanoparticle detection in complex media

Nanoparticle (NP) tracking in complex media is still a challenge since NP concentrations are expected to be low compared to elemental background levels as it can be found in environmental matrices. This study presents a new method for radiolabeling of commercial silver nanopowder (Ag0-NPs, dp < 100 nm) with 110mAg radionuclides (t1/2 = 249.9 days) that provide an adequate time frame for particle detection, localization, and tracking under various experimental conditions. The radiolabeling procedure insures high efficiency, stability, and consistency of important particle properties such as size and morphology. Detection of Ag0-NP in concentrations as low as 125 ng kg−1 could be reached. For the first time, an appropriate tool for life-cycle studies of commercial Ag0-NPs is provided without changing chemical composition of the material. This is of great importance e.g., for research in the field of nanotoxicology.

Facile chemical synthesis of nano-silver powders for printable electronics applications

In this article, a simple and reproducible technique for the synthesis of silver nanoparticles in organic phase without using external reducing agents is reported. The organic phase contains silver acetate as precursor, oleic acid and oleyl amine as capping molecules and diphenyl ether as solvent. Monodispersed silver nanoparticles with an average size of 5 nm could be easily synthesised at large scale and it was possible to isolate the particles suitable for electronics applications. The formation of silver nanoparticles has been characterised in terms of optical absorption, transmission electron microscopy images and small-angle X-ray scattering. Recovered silver nanoparticles reveal X-ray diffraction of a well grown-up fcc-Ag lattice. Chemical and thermal characterisations of silver nanopowders were carried out using X-ray photoelectron spectroscopy and thermogravimetric analysis, respectively. For the latter purpose, concentrated dispersions of silver nanoparticles were prepared and used for depositing uniform thin layers. Thin films were sintered at low temperature to obtain conductive films and the films were characterised using scanning electron microscope. Electrical conductivity of the conductive films was in the range 2–3 × 104 S cm−1.

Effects of Different Reducing Agents and Protective Agents on the Preparation of Nano-Silver Powder

Solution chemical reduction method is a means which used reducing agent in aqueous or organic systems to deoxidize silver ions. Its essence is an integrated process of the electrochemistry, thermodynamics, kinetics and fluid dynamics and so on. The process determines the physical and chemical properties such as the size distribution of powder, purity and reunion situations, etc. Nano-silver powder has high surface activity and catalytic properties, and is widely used to a lot of fields. So it has very important realistic significance to study the preparation method. In this paper, nano-silver powder was prepared with industrial AgNO3 as raw materials, sodium borohydride or hydrazine hydrate as reducing agent, polyvinyl alcohol, SDBS or polyvinylpyrrolidone(PVP) as the surface protective agent by solution chemical reduction method. The influences of different reducing agents and protective agents on the preparation of nano-silver were analyzed. The results from the XRD diffraction analysis and TEM show that it can be obtained high purity flake nano-silver in the reaction temperature range of 50-60°C.

Electrical conductivity and magnetic properties of core-shell silver-coated magnetite composite nanoparticles

Abstract

Electrolytic Synthesis and Characterization of Silver Nanopowder

This work reports a simple, novel, cost effective and eco-friendly electrolytic synthesis of silver nanoparticles using AgNO 3 as metal precursor. The synthesis rate is much faster than other methods and this approach is suitable for large scale production. They are characterized by XRD, SEM and FT-IR techniques to analyze size, morphology and functional groups. XRD studies reveal a high degree of crystallinity and monophasic Ag nanoparticles. Their particle size is found to be 24 nm and specific surface area (SSA) is 24 m 2 g -1 . Analysis of Ag nanoparticles SSA reports that increasing their SSA improves their antibacterial actions. Microbiology assay founds that Ag nanoparticles are effective against E.coli and B.megaterium bacteria. SSA of bacteria analysis reveals that it plays a major role while reacting with antimicrobial agents.

Thermal characterization of screen printed conductive pastes for RFID antennas

Abstract Thermal resistance is an essential aspect of electronic circuits designing. It leads to unexpected changes in electronic components during their work. In this study, new materials for screen printed RFID tag's antennas were characterized in terms of their resistance to thermal exposure. Polymer materials containing silver flakes, silver nanopowder, carbon nanotubes or conductive polymer PEDOT:PSS were elaborated and used for antenna printing on flexible materials. In order to verify their long term susceptibility to damages caused by the changing environmental conditions, the temperature cycling test was used in three different temperature ranges: +65 °C, −12 °C, −40 °C/+85 °C (3 h in each temp., dwell time 1 h). The highest durability to thermal exposure exhibited the paste with carbon nanotubes dispersed in poly(methyl methacrylate) PMMA and the lowest one – the paste with conductive polymer PEDOT:PSS.

Study on Properties of Conductive Adhesive Prepared with Silver Nanoparticles Modified by Silane Coupling Agent

Abstract Silver nanoparticles modified by silane coupling agent KH-560 were used as conductive filler to prepare conductive adhesive at 180 °C in epoxide resin vehicles. The as-modified Ag nanoparticles and conductive adhesive were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC). The effects of silver content and curing time on the properties of conductive adhesive were studied. The results show that KH-560 modified Ag powders with a particle size of approximately 20 nm are uniformly dispersed and KH-560 molecules are adsorbed on silver particle surface. Silver content and curing time could influence the properties of conductive adhesive significantly. The bulk resistivity of conductive adhesive with 55 wt% silver nanoparticle and curing time of 15 min reaches a minimal value of 2.5×10−3 Ω·cm. Compared with the conductive adhesive filled with unmodified silver nano-powders, the bulk resistivity of conductive adhesive filled with modified silver nano-powders increases by 3–5 times.