Small Silver Particles Research Articles

A Systematic Knowledge of Nanoparticles and Nanotechnology - A Review

The main aim is to describe the journey to beautiful and useful word Nano. Nano stands for one billionth. In science & technology, Nano stands for one billionth of meter, 1nm-10-9 m. Nanoparticles and nanotechnology words are relatively new but nanoparticles themselves has been around and studied long before the word were used. The beautiful colours of stained glass windows are a result of the presence of small metal oxide clusters in glass, having a size comparable to the wavelength of light. Particles of different sizes scatter different wavelength of light, imparting different colours to the glass. In photography the small colloidal particles of silver are a part of the processes of image formation and water at ambient temperature consists of clusters of hydrogen bonded water molecules. The description of variation of properties of nanoparticle with size, practical application of nanotechnology, uses in defence and biotechnology and as well as disadvantage of nanotechnology are given in this article.

In situ discovery on the formation of supported silver catalysts for ethylene epoxidation

Silver particles supported on alumina are the main industrial catalysts for ethylene epoxidation. Silver catalysts are usually produced by an impregnation method followed by thermal decomposition. Although the decomposition process determines the structures and properties of silver catalysts, we are short of information on this high temperature process. Herein we employed a confocal laser scanning microscope (CLSM) equipped with a heating stage to disclose the thermal decomposition process of silver precursor towards the preparation of high selective silver catalysts. It is found that the formation of silver catalysts experiences two steps: crystallization and decomposition. The crystallization occurs at the temperature below 80℃, resulting in the formation of silver complex. Further heating the sample to 140℃, leads to the formation of silver particles at alumina wafers. The atmosphere has a significant effect on the formation and performance of catalysts. When the samples are heated in the nitrogen, small silver particles with similar size are formed, which leads to a high selectivity of ethylene epoxidation. The role of thermal atmospheres on the size and property of silver catalysts is discussed in this paper.

Molecular Dynamics Simulation of Sintering Densification of Multi-Scale Silver Layer.

Based on molecular dynamics (MD), in this study, a model was established to simulate the initial coating morphology of silver paste by using a random algorithm, and the effects of different sizes of particles on sintering porosity were also analyzed. The MD result reveals that compared with the sintering process using large-scale silver particles, the sintering process using multi-scale silver particles would enhance the densification under the same sintering conditions, which authenticates the feasibility of adding small silver particles to large-scale silver particles in theory. In addition, to further verify the feasibility of the multi-scale sintering, a semi in-situ observation was prepared for a sintering experiment using micro-nano multi-scale silver paste. The feasibility of multi-scale silver sintering is proved by theoretical and experimental means, which can provide a meaningful reference for optimizing the sintering process and the preparation of silver paste for die-attach in powering electronics industry. In addition, it is hoped that better progress can be made on this basis in the future.

Induced Optical Bistability in Small Metal and Metal Coated Particles with Nonlinear Dielectric Functions

The theoretical and numerical study of the enhancement of the amplitude of the incident electromagnetic radiation in small metal ellipsoidal particles and spherical dielectric particles covered by a metal shell with nonlinear dielectric functions is carried out. If the frequency of the external radiation approaches the frequency of surface plasmons of a metal, the local field in the particle considerably increases. At intense incident electromagnetic fields (laser radiation), it is necessary to consider the nonlinear part of the dielectric functions of a metal and a dielectric. This results in the induced optical bistability (IOB) when one value of the amplitude of the incident field initiates three values of the local field in a particle. The domains of IOB are specified in the case where the radiation wavelength is much larger than the typical size of particles. The range of external fields and the IOB frequency are specified. A decrease of the IOB domain and an increase of the critical fields with increase in the damping of plasmon vibrations are discussed. The results of numerical computations for typical small silver particles are presented graphically.

Optical properties of antimony-borate glass rods co-doped with Eu3+/Ag+ ions

This paper presents the results of research on the luminescent properties of antimony-borate glass rods doped with europium and silver ions. The reduction of silver ions to the form of nanoparticles was carried out and the occurrence of localized plasmon resonance was demonstrated, which caused changes in the Eu3+ luminescence signal at a wavelength of 613 nm. The effect of the concentration of silver ions dopant at a constant content of europium ions on the luminescence and absorption characteristics of the produced samples was investigated. In the examined doping range, no large dependencies of spectral changes as a function of the concentration of silver ions were found. A clear quenching of the luminescence was observed due to the heating time of the doped glass matrices for the energy transition (5D0 → 7F2). Full Text: PDF ReferencesS. Kuzman, J. Perisa, V. Dordevic, I. Zekovic, I. Vukoje, Z. Antic and M. D. Dramicanin, "Surface Plasmon Enhancement of Eu3+ Emission Intensity in LaPO4/Ag Nanoparticles", Materials 13, 3071 (2020). CrossRef V.P. Prakashan, M.S. Sajna, G. Gejo, M.S. Sanu, A.C. Saritha, P.R. Biju, J. Cyriac and N.V. Unnikrishan, "Surface Plasmon Assisted Luminescence Enhancement of Ag NP/NWs-Doped SiO2-TiO2-ZrO2:Eu3+ Ternary System", Plasmonics 14, 673 (2019). CrossRef O. Malta, P. Santa-Cruz, G. Sa and F. Auzel, "Fluorescence enhancement induced by the presence of small silver particles in Eu3+ doped materials", J. Lumin., 33, 261 (1985). CrossRef O. Malta, P. Santa-Cruz, G. Sa and F. Auzel, "Time evolution of the decay of the 5Do level of Eu3+ in glass materials doped with small silver particles", Chem. Phys. Lett, 116, 396 (1985). CrossRef J. Zmojda, M. Kochanowicz, P. Miluski et al., "The influence of Ag content and annealing time on structural and optical properties of SGS antimony-germanate glass doped with Er3+ ions", Journal of Molecular Structure 1160, 428 (2018). CrossRef Ki Young Kim, Plasmonics: Principles and Applications (Croatia, InTechOpen 2012) CrossRef M.R. Dousti, M.R. Sahar, S.K. Ghoshal et al., "Up-conversion enhancement in Er3 +-Ag co-doped zinc tellurite glass: Effect of heat treatment", Journal of Non-Crystalline Solids 358, 2939 (2012). CrossRef I. Soltani, S. Hraiech, K. Horchani-Naifer et al., "Effect of silver nanoparticles on spectroscopic properties of Er3+ doped phosphate glass", Optical Materials 46, 454 (2015). CrossRef R. Schneider, E.A. de Campos, J.B.S. Mendes, J.F. Felix, P.A. Santa-Cruz, "Lead–germanate glasses: an easy growth process for silver nanoparticles and their promising applications in photonics and catalysis", RSC Advances 7 (66), 41479 (2017). CrossRef

РЕЛАКСАЦИЯ ОСТАТОЧНЫХ НАПРЯЖЕНИЙ В ДЕКАЭДРИЧЕСКИХ ЧАСТИЦАХ ПУТЕМ ОБРАЗОВАНИЯ ЦЕНТРАЛЬНОЙ СФЕРИЧЕСКОЙ ПОРЫ

Small metal particles with a body-centered crystal lattice (BCC) often take the form of polyhedrons with fifth-order symmetry axes such as the icosahedron, decahedron, and pentagonal prism. The quintic symmetry axes, forbidden by the traditional crystallography laws, cause inhomogeneous elastic stress and strain in these particles. Under certain conditions, these stress and strain could relax through the change in the particle structure: the formation of partial and perfect dislocations, misfit layers, and the nucleation of cracks and voids. Within the quasi-equilibrium energy approach, the authors proposed a theoretical model of residual stress relaxation in decahedral particles due to the formation of a central spherical void. The explicit analytical expressions for energies of solid and hollow decahedral particles are found. The elastic energy of a hollow decahedral particle is defined as the work spent on the nucleation of a positive wedge disclination with the power ω≈0.0163 rad (≈7°20') in the elastic spherical shell under its own stress field. The authors determined the change in the surface energy due to the formation of a void considering the influence of the relaxation effect of the first coordination sphere surrounding the vacancy on the particle volume change. The energy change of decahedral particles during the formation of a spherical void is calculated and the optimal and critical parameters of this process are determined. The study shows that there some critical radius of a particle, if reached the formation of the central spherical void becomes energetically favorable. Moreover, the study shows that a pore germ will grow until it reaches a certain optimal size corresponding to the greatest change in the system energy. The numerical calculations correspond with experimental observations of unstable voids in the rather small silver and gold decahedral particles with the diameter of 30–40 nm and stable voids in relatively large copper decahedral particles with the diameter of ~1 μm.

The Ability of Ginger Rhizome (Zingiber officinale Rosc) Extract in Producing of Silver Nanoparticles and the Antibacterial activity of these nanoparticles

Recently, using plant extract as a reducing agent for nanosilver particle synthesis hasbeen focused. This is a green technology utilizing the ready material in the nature to create thenanoparticles with good properties and uniqe quality. In this study, ginger rhizome extract wasused to reduce the silver cation (Ag + ) to silver (Ag o ) as nanoparticles with uniqe quality and evendistribution in the solution. The size of the particles varied in the range of 20-40 nm. Reactionconditions were investigated and optimized with AgNO 3 concentration of 3mM, extractsolution/AgNO 3 solution of 1/5, temperature of 80˚C, pH of 12 and reaction time of 30 min. Theresults obtained from the antibacterial assays showed that silver nanoparticle solution hadantibacterial ability with an average effective diameter of 10 mm. It also indicated that theantibacterial activity of silver nanoparticle solution on the Gram (-) bacterium (E. coli) is betterthat on Gram (+) bacterium (S. aureus). In conclusion, we suggest that the ginger rhizome extractcan be used to produce silver nanoparticles in mild reaction conditions; the silver nanoparticlesolution expressed as a quite good antibacterial agent and therefore could be applied in decreasingthe effects of deleterious bacteria.Keywords
 Silver nanoparticle, plant extract, antibacterial, Zingiber officinale Rosc.
 References
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Structure Sensitivity of Silver-Catalyzed Ethylene Epoxidation

The influence of particle size (20–200 nm) of Ag/α-Al2O3 catalysts for epoxidation of ethylene to ethylene oxide (EO) under industrial conditions was investigated. Small silver particles up to ∼40 ...

Ångstrom‐Scale Silver Particles as a Promising Agent for Low‐Toxicity Broad‐Spectrum Potent Anticancer Therapy

AbstractCancer incidence is rising, and the efficacy of current available anticancer agents is limited by severe dose‐limiting toxicities and drug resistance problems. Nanoparticles are heralded as the next frontier in cancer treatment. Here, a pure physical method is used to efficiently fabricate very small silver particles even approaching the Ångstrom (Ång) dimension. Fructose is used as a dispersant and stabilizer to coat the Ång‐scale silver particles (AgÅPs). Functional and mechanistic studies demonstrate that fructose‐coated AgÅPs (F‐AgÅPs) can enter and accumulate in multiple cultured cancer cell lines to induce apoptotic death, whereas most normal cells are resistant to the efficacious dose of F‐AgÅPs; in vivo, intravenous administration of F‐AgÅPs potently inhibits the growth of pancreatic and lung cancer xenografts in nude mice, without inducing notable toxic effects on the healthy tissues. The results suggest the promising potential of F‐AgÅPs as a potent, safe, and broad‐spectrum agent for the cancer treatment.

Concentration- and Time-Dependent Cytotoxicity of Silver Nanoparticles on Normal Human Skin Fibroblast Cell Line

Background: A wide use of Silver Nanoparticles (AgNPs) in consumer products, industry, pharmaceuticals, and medical sciences, including dermatology, has always caused concerns related to its adverse effects on the environment and human safety. Nano-sized particles can be uptaken by the body through various routes, especially the skin, which is the widest organ and the first contact surface for different nanomaterials and other foreign agents. Objectives: The aim of this investigation was to assess the viability of a vulnerable normal skin cell line to cytotoxicity of AgNPs with the same effective size and concentrations used for various microbial agents, such as Candida species. Methods: Synthesized AgNPs were characterized using UV-visible absorption spectroscopy, X-ray diffraction, Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM). Different concentrations of the aqueous colloidal AgNPs (2.17 to 69.5 µg/mL) were tested on normal Human Skin Fibroblast (HSF) cell line using MTT assay after 24 and 48 hours of exposure. Results: The analysis demonstrated that the synthesized AgNPs were mainly spherical with an average size of 6.03 nm. The MTT findings showed a significant concentration- and time-dependent manner in the reduction of cell viability. The calculated IC50 values were 30.64 and 14.98 µg/mL for 24 and 48 hours of incubation, respectively. Conclusions: The cytotoxic effect of AgNPs was higher for Human Skin Fibroblast cells after 48 hours of exposure compared with 24 hours. According to the observed results, small nano-sized silver particles could potentially have cytotoxic effects on normal cells, especially at high concentrations and prolonged exposure times.

Effective and regenerable Ag/4A zeolite nanocomposite for Hg0 removal from natural gas

The silver loaded adsorbents has been demonstrated to be an exciting approach towards Hg0 removal from natural gas streams, its Hg0 removal efficiency and capacity is closely related to the valence state, particle size and dispersity of silver particles. This study focused on chemical reduction methods in aqueous solutions to synthesize Ag/4A zeolite, and the influences of ultrasonic and protective additives were investigated to reduce the size of silver particles. The characterization results showed that silver particles are loaded on the surface of 4A zeolite with highly dispersed elemental form, ultrasonic and addition of stearic acid as protective additives are the effective ways to produce small nano-scale silver particles close to 15 nm. Meanwhile, the silver particles on the surface of Ag/4A zeolite are the active sites for Hg0 adsorption which can react with Hg0 to form Ag-Hg amalgam alloy. The silver lattices disappeared from the outer boundary to the interior of the particles after Hg0 adsorption, which indicated that the Hg0 firstly reacts with the nano-scale silver on the surfaces and then gradually penetrates into the interior of silver particles. The Hg0 removal efficiency of prepared Ag/4A zeolite adsorbents was higher than 96% after 200 min adsorption at 30 °C, and adsorption capacity reached to 5.985 mg/g. Furthermore, the regeneration and reutilization results indicated that the Hg0 adsorption performance remained stable after 5 reuse cycles.

Synthesis of Ag/rGO composite materials with antibacterial activities using facile and rapid microwave-assisted green route.

The present paper represents a facile and rapid synthesis of silver-reduced graphene oxide Ag/rGO (Ag/reduced graphite oxides) composites with the help of microwave irradiation. This is a rapid green route requiring power microwave irradiation only 400 W(30 s) and 200 W (60 s) for the uniform Ag nanoparticles with average diameter of ~10 nm embedded on rGO sheets. In the microwave irradiation process, rGO samples absorb electromagnetic energy to be heated rapidly due to their intrinsic dielectric and conductive losses. Local hot sheets appear in aqueous solution, facilitating homogeneous nucleation, as well as the grain growth of Ag crystallites throughout the rGO sheets. The obtained Ag/rGO composites exhibited significant antibacterial property towards Gram-negative bacteria (E. coli and P. aeruginosa), Gram-positive bacteria (S. aureus and Enterococcus), and white rot fungus. The minimum bactericidal concentration of the Ag /rGO nanocomposite against E. coli was about 1 μg/mL. Strong interaction between Ag/rGO composites and bacteria contributed to the totally non-activity of bacteria. We designed Ag/rGO nanocomposite with excellent antibacterial activities by facile andrapid microwave-assisted green route. In Ag/rGO nanocomposite, the morphology and size distributions of Ag particles anchored on the rGO sheets can controlled via the microwave irradiation power and time. The results suggested that in the microwave field, GO reduced into unique rGO sheets and uniform AgNPs with average size of 12 nm can be decorated on rGO sheets at 30 s and at 200 W, respectively. we successfully demonstrated small silver particles anchored on graphene displayed great antibacterial activities against Gram-negative bacteria (E. coli and P. aeruginosa), Gram-positive bacteria (S. aureus and Enterococcus) and white rot fungus. Ag/rGO nanocomposites may have potential applications as antibacterial agent for daily life.

A novel method to prepare self‐lubricity of Si3N4/Ag composite: Microstructure, mechanical and tribological properties

AbstractSi3N4/Ag composites were firstly prepared through SPS technology, using Si3N4 and AgNO3 as raw materials. Utilizing the coordination bonding of Ag+ ions with nitrogen atoms of Si3N4, in situ generated Ag particles about 1 μm were tightly anchored on Si3N4 surface, thereby preventing the outflow of silver during sintering process. Meanwhile, smaller silver particles about 20 nm were located at the grain boundaries of Si3N4, which effectively improved the mechanical and tribological properties of Si3N4‐based composites. Finally, the Si3N4/Ag composites reinforced by Ag particles showed a friction coefficient of 0.48 ± 0.01, wear rate of 1.79 × 10−6 mm3 N−1 m−1 and fracture toughness of 7.05 ± 0.2 MPa m1/2, respectively.

Real-time investigations of structural and optical changes in photochromic Ag/TiO2 nanocomposite thin films under laser irradiation

Photochromic reaction dynamics in silver nanoparticles embedded in mesoporous titanium dioxide thin films is investigated by combining real-time grazing incidence small-angle x-ray scattering (GISAXS) and optical transmission measurements during UV–visible laser exposure cycles. While GISAXS probes changes in the particle size distribution, transmittance measurements are sensitive to spectral changes induced by photo-activated processes. Our results reveal a repeatable photochromic behavior with a good correlation in terms of kinetics between the morphological and optical fluctuations. Visible laser irradiation at 532 nm induces a preferential photo-dissolution of small silver particles, which in turn causes an increase in transmittance near the excitation wavelength. Furthermore, the photo-dissolution process can be significantly accelerated and amplified by associating visible laser with x-ray irradiation. Under UV laser irradiation at 360 nm, the bleaching process can be reverted by photocatalytic reduction with the mesopores in the TiO2 film acting as molds, which have the ability to confine the nanoparticle growth. However, in the irradiation conditions used in the present study, it appears that the photocatalytic growth of silver nanoparticles is slower than the photo-dissolution process, whereas its efficiency gradually degrades throughout the exposures to UV light.

Facile and Cost Effective Synthesis of Oxide-Derived Silver Catalyst Electrodes via Chemical Solution Deposition for CO2 Electro-Reduction

Electrochemical CO2 reduction to useful fuels is a promising strategy for the sustainable energy production. However, because CO2 reduction reaction involves sluggish kinetics, the development of high performing catalyst is a first priority for the success in this system. Herein, cost effective fabrication of oxide-derived silver catalyst for CO2 electro-reduction was successfully prepared by simple chemical solution deposition involving the following steps: (i) spin-coating of precursor solution, (ii) oxidation by air-annealing, and (iii) electrochemical reduction. The prepared silver catalyst achieved 83.7% of CO Faradaic efficiency at − 1.19 VRHE with an outstanding mass activity of 465.04 A g− 1 which was originated from the unique features of the catalyst as well as precursor solution. With the introduced fabrication method, the precursor solution containing relatively low silver concentration was preferred to form small silver particles, resulting in high catalytic activity. We anticipate the developed method to be widely applied for the preparation of oxide-derived metal catalysts and metal alloy nanostructured catalysts in advanced CO2 conversion system.

Evolution of the morphology of small pentagonal particles and microcrystals during the electrodeposition of silver in a potentiostatic regime

A procedure for obtaining icosahedral and decahedral small particles and microcrystals of silver is presented. The evolution of the morphology during growth is studied in detail. Mechanisms of the relaxation of elastic stress fields in small silver particles and microcrystals with pentagonal symmetry are found experimentally.

Two-step photochemical inorganic approach to the synthesis of Ag-CeO2 nanoheterostructures and their photocatalytic activity on tributyltin degradation

Abstract Herein, we report a simple, sustainable and low-cost approach to design Ag-CeO 2 nanoheterostructures in pure aqueous and ethanol containing aqueous solutions via photochemical UV-light driven process with no capping agents nor stabilizers required. To this end, photochemically synthesized CeO 2 nanoparticles were applied as photoactive compounds in order to generate formation of metallic silver nanoparticles. Irradiation of deaerated CeO 2 suspensions in the presence of Ag + resulted in the rise of a strong surface plasmon resonance band with a maximum at 393–422 nm in the absorption spectra of the solutions, indicating formation of small metallic silver particles. Faster formation of Ag nanoparticles with the lower amount of silver precursor being required was observed when ethanol was introduced to the reaction solution before the irradiation. This implies that oxidative reactions can be strongly suppressed in deaerated ethanol containing solutions with respect to the pure aqueous media. Not only was the overall efficiency of the process remarkably increased by the use of alcohol, but also smaller and more uniform silver nanoparticles with a size comparable to that of ceria nanoparticles (around 15 nm) were formed when compared to those synthesized without radical scavengers as revealed by TEM analysis. The proposed photochemical approach enables the production of silver-semiconductor system without employing organic stabilizers, thus resulting in formation of nanoparticles with “clean”, highly reactive metal surface. The as-synthesized silver-ceria nanoheterostructures demonstrated enhanced visible light driven photocatalytic activity on tributyltin (TBT) degradation if compared to pure ceria nanoparticles.

Polarization of enhanced light transmittance by small elongated silver particles array in glass

We report an optical polarizer device with enhanced transmittance by small elongated silver particles array in glass with antireflection coatings. The device consists of periodically distributed elongated silver nanoparticles inside the transparent Ag-doped photosensitive glass. Mie theory and dipole theory are well used to explain the physics interrelationships between input light and elongated silver particles. A three dimensional model is designed to simulate and calculate the polarization properties based on FEM method. The polarization properties are mainly influenced by the parameters of the geometry structure of elongated silver particles array in the glass. With optimized design parameters of aspect ratios, filling factors, antireflection coating depths, sizes of silver nanoparticles, the transmittance is enhanced with high extinction ratio over a wide wavelength range. In our calculations, the transmittance is greater than 87% with extinction ratio more than 40dB by use of an antireflection film over the wavelength range from 650nm to 1100nm. Moreover, the maximum increase of enhanced polarized transmittance is over 20% in the near infrared region with extinction ratio over 40dB. The approach and results can be guidance for design, manufacture and application of the optical polarizer micro-nano devices.

Enhancement of local electric field in core-shell orientation of ellipsoidal metal/dielectric nanoparticles

In this paper it is shown that the enhancement factor of the local electric field in metal covered ellipsoidal nanoparticles embedded in a dielectric host matrix has two maxima at two different frequencies. The second maximum for the metal covered inclusions with large dielectric core (small metal fraction $p$) is comparatively large. This maximum strongly depends on the depolarization factor of the core $L_{z}^{(1)}$, keeping that of the shell $L_{z}^{(2)}$ constant and is less than $L_{z}^{(1)}$. If the frequency of the external radiation approaches the frequency of surface plasmons of a metal, the local field in the particle considerably increases. The importance of maximum value of enhancement factor $|A|^{2}$ of the ellipsoidal inclusion is emphasized in the case where the dielectric core exceeds metal fraction of the inclusion. The results of numerical computations for typical small silver particles are presented graphically.

Oxygen Reduction, Transport and Separation in Low Silver Content Scandia-Stabilized Zirconia Composites

Dense composites of silver and Sc-stabilized ZrO2 (Ag-ScSZ) are manufactured from ScSZ sub-micrometric particles coated with silver using Tollens’ reagent. A composite with 8.6 vol % of silver exhibits metallic conductivity of 186 S cm−1 and oxygen flux of 0.014 μmol cm−2 s−1 at 600°C for a 1-mm thick membrane when used as a pressure-driven separation membrane between air and argon. To gain insight into the role of oxygen transport in Ag and ScSZ, a dense non-percolating sample (Ag 4.7 vol%) is analyzed by impedance spectroscopy and the transport of oxygen through both phases is modelled. Oxygen transport takes place in both silver and ScSZ but it is still dominated by transport in the ionic conductor and therefore a large volume fraction of the ion conductor is beneficial for the separation. The oxygen transport in the silver clusters inside the composite is dominated by diffusion of neutral species and not by the charge transfer reaction at the interface between ScSZ and Ag, yet small silver particles on the surface improve the reduction of oxygen. Oxygen reduction is highly promoted by silver on the surface and there are no limitations of charge transfer at the interface between silver and ScSZ.