Number Of Silver Nanoparticles Research Articles

Dependence of the size and number of silver nanoparticles on the ligand concentration in the reaction system

Dependence of the size and number of silver nanoparticles on the ligand concentration in the reaction system

Empowering the boiling condition of Argon flow inside a rectangular microchannel with suspending Silver nanoparticles by using of molecular dynamics simulation

This paper presents influences of suspending a different number of Silver nanoparticles on the flow parameters of Argon base fluid, which is under boiling condition inside a cubic microchannel. Argon flow is enforced by an external force of 0.002eV/A°. Also, a constant temperature of 108K is applied to the walls of the microchannel to prepare boiling flow condition. Presence of Silver nanoparticles empowers heat transfer rate and brings stronger phase change. It is the reason of sooner translocation of base fluid atoms from the vicinity of microchannel walls to the center of the microchannel in z-direction. This phenomenon enhances fluid temperature whereas; it is not in favor of external driving force, which supports the velocity of fluid flow inside microchannel in x-direction. Despite fluctuation in density profiles, it is indicated that Silver nanoparticles are never attached together. Also, the influence of nanoparticles on the density fluctuation is significant at lower time steps. Afterward, the statistical approach is employed to present accurate results. It was found that presence of two, four and six nanoparticles into Argon base fluid increases summation of density as much as 20%, 37% and 67%, Whereas; they bring enhancement in summation of temperatures as much as 20%, 49%, and 84% respectively. Finally, it is concluded that investment on preparing nanofluid by suspending two nanoparticles into Argon base fluid is not economical for practical application; while, suspending four and six numbers of Silver nanoparticles is applicable for practical application.

Modeling and simulation of contact parameters of elliptical and cubic nanoparticles to be used in nanomanipulation based on atomic force microscope

Regarding the contact mechanics of smooth nanoparticles, two new geometries, specifically elliptical and cubic are chosen for nanoparticles. The results of elliptical contact simulation show that the JKR theory induces a greater indentation depth in both contact geometries since it includes the adhesion forces. Moreover, the Jamari theory shows a lesser indentation depth because it assumes larger contact area. The results of cubic nanoparticles simulation exhibit a significant difference between the contact of tip and nanoparticle compared to the contact of nanoparticle and surface. This can be attributed to the large contact area between the cubic nanoparticle and the reference surface. The JKR and DMT theories, however, show greater indentation depths in the tip contact with nanoparticle. Furthermore, the Lundberg theory yields the maximum indentation depth in the nanoparticle contact with reference surface. Finally, in order to validate the results, experimental and FEM approaches are incorporated. Concerning the experimental results, a certain number of silver nanoparticles are placed on a polystyrene surface. After obtaining the experimental force-displacement curves, the results of presented models are compared with them. The experimental results indicate that for silver nanoparticles and polystyrene surface, the Hertz theory with 1.11% of error and the JKR theory with 8.7% of error show the best output, respectively. Regarding rough nanoparticles contact, the geometry of roughness are taken as elliptical. Meanwhile, analytical relations are presented to solve force and contact area integrals while noting the problem dimensions. The results of simulation show that the JKR theory yields the highest roughness force, followed by the Hertz and Jamari theories, and regarding rough contact area, the Hertz theory creates the largest contact area, followed by the Jamari and JKR theories. The presented analytical method is compared with numerical results as a means of validation.

Properties of Bacterial Cellulose Composites with Silver Nanoparticles

Composites of bacterial cellulose, which were synthesized in a culture of the strain of acetic acid bacteria Komagataeibacter xylinus VKPM B-12068, with silver nanoparticles were produced hydrothermally by varying the concentrations of AgNO3 in the medium. The presence of silver in the composites was confirmed by elemental analysis. An increase in the number of silver nanoparticles in the composite from 1.08 to 9.1 wt % (from 0.044 to 0.370 mg/cm2) was shown under increasing AgNO3 concentration in the medium from 0.0001 to 0.01 M. The structure, properties of the surface, and the physicochemical properties of the composites depending on the silver content were investigated using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and a water contact-angle measurement system. Using the disk-diffusion method, it was shown that the resulting composites have a pronounced antibacterial activity against pathogenic microflora E. coli, Ps. eruginosa, and St. aureus.

Factors influencing the preparation of silver-coated glass frit with polyvinyl-pyrrolidone

In this work, a new electroless silver plating method for the synthesis of silver-coated glass frit composite powders with good morphology has been proposed and the polyvinyl-pyrrolidone (PVP) was used the activating agent. It was found that the weight ratio of PVP to glass frit affected the distribution and number of silver nanoparticles. Moreover, the loading capacity of the glass frit, the pH value and reaction temperature could influence the size of the silver nanoparticles and morphology of silver on the surface of glass frit. The as-prepared silver-coated glass frit was used to prepare a silver paste using an optimized process to form silver nanoparticles with uniform size and high density. The silver paste with silver-coated glass frit increased the photovoltaic conversion efficiency of silicon solar cells by 0.271% compared with the silver paste prepared with pure glass frit. The silver nanoparticles can promoted the precipitation of Ag crystallites on the silicon wafer. Therefore, the silver-coated glass frit can further optimize and enhance the electrical performance of solar cells.

Self-organization processes and synthesis of nanostructured silver microparticles in AgNO3 solutions with variable pH values

The morphology of micrometer-sized silver particles obtained by liquid-phase chemical reduction of silver nitrate with ascorbic acid depends appreciably on the solution pH. The synthesis carried out at 100°C for 20 min at pH 9 yields anisotropic faceted nanocrystalline particles, while the synthesis at pH = 5–8 results in self-assembly to give microspheres representing close-packed aggregates of a huge number of silver nanoparticles with a cauliflower structure.

Variations of antibacterial activity and silver characteristic of silver‐containing activated carbon fibers undergoing cyclic antibacterial tests

Seven cycles of antibacterial tests were performed on silver‐containing activated carbon fibers derived from liquefied wood (WACF/Ag) to investigate the variations of their antibacterial activity and silver characteristics. The results showed that all the WACF/Ag had the excellent antibacterial durability. Less silver ions were released from WACF/Ag prepared at the soaking concentration of 0.2 mol/L. Both silver and silver ion content followed a decreasing trend with an increase in cycle number of antibacterial tests, and the significant drop occurred in the first cycle. The silver on the surface and in mesopores was almost removed in the first cycle of antibacterial tests, while that in micropores was released slowly with increasing cycle number of antibacterial tests. The schematic illustrations for WACF/Ag revealed that the number of silver nanoparticles in micropores had the determined effect on the antibacterial durability. POLYM. COMPOS., 38:1404–1411, 2017. © 2015 Society of Plastics Engineers

Rapid in situ synthesis of silver nanoparticles on the distal facet of a fiber by laser-induced photo-reduction

We explore a novel and rapid route for fabricating silver nanoparticles on the distal facet of an optical fiber. The reduction of neutral silver particles relies on the reaction between silver ions and organic free radicals initiated by the photolysis of photoinitiators. A similar approach has been extended to the fabrication of a silver nanoparticle array at the extremity of a fiber bundle. The size and number of silver nanoparticles can be tuned by controlling the laser exposure doses. The results of the synthesis can be envisaged via in situ measurement of their optical transmission rate after the photosynthesis process.

Direct functionalization of an optical fiber by a plasmonic nanosensor

We explore a rapid route for fabricating silver nanoparticles (NPs) at the end of an optical fiber. The size and number of silver NPs can be controlled by varying the exposure doses. The effect of the refractive index of different solvents on the extinction spectra have been studied as a proof of concept of a fiber integrated plasmon-based sensor.

Exposure assessment of workplaces manufacturing nanosized TiO2 and silver

With the increased production and widespread use of nanomaterials, human and environmental exposure to nanomaterials is inevitably increasing. Therefore, this study monitored the possible exposure to nanoparticles at workplaces that manufacture nano-TiO2 and nano-silver. To estimate the potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using a scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers handle nanomaterials. The gravimetric concentrations of TiO2 ranged from 0.10 to 4.99 mg/m3, which were lower than the occupational exposure limit 10 mg/m3 set by the Korean Ministry of Labor or American Conference of Governmental Industrial Hygienists (ACGIH). Meanwhile, the silver metal concentrations ranged from 0.00002 to 0.00118 mg/m3, which were also lower than the silver dust 0.1 mg/m3 and silver soluble compound 0.01 mg/m3 occupational exposure limits set by the ACGIH. The particle number concentrations at the nano-TiO2 manufacturing workplaces ranged from 11,418 to 45,889 particles/cm3 with a size range of 15–710.5 nm during the reaction, although the concentration decreased to 14,000 particles/cm3 when the reaction was stopped. The particle concentrations at the TiO2 manufacturing workplaces increased during the reactor and vacuum pump operations, and during the collection of the synthesized TiO2 particles. Similarly, the particle concentrations at the silver nanoparticle manufacturing workplaces increased when the sodium citrates were weighed or reacted with the silver nitrates, and during the cleaning of the workplace. The number of silver nanoparticles in the samples obtained from the workplace manufacturing silver nanoparticles using induced coupled plasma ranged from 57,789 to 2,373,309 particles/cm3 inside the reactor with an average size of 20–30 nm and 535–25,022 particles/cm3 with a wide range of particle sizes due to agglomeration or aggregation after the release of nanoparticles into the workplace air. In contrast, the silver nanoparticles manufactured by the wet method ranged from 393 to 3526 particle/cm3 with an average size of 50 nm. Thus, when taken together, the TiO2 and silver nanoparticle concentrations were relatively lower than existing occupational exposure limits.

In situ preparation, electrospinning, and characterization of polyacrylonitrile nanofibers containing silver nanoparticles

AbstractSilver nanoparticles were prepared from a polyacrylonitrile (PAN)/N,N‐dimethylformamide solution of silver nitrate (0.05–0.5 wt %) with light treatment (xenon arc) to reduce Ag+ ions into Ag0. The formation of silver nanoparticles in the PAN solution and the effect of treatment time on the numbers of silver nanoparticles, their average diameter and size distribution were investigated by UV–visible spectroscopy. In addition, the average size of silver nanoparticles and their shapes in colloidal solution were determined by transmission electron microscopy images and found to be on the order of 10 nm. The resulting solution was electrospun into PAN nanofibers. An increase in the salt concentration led to decreases in the nanofiber diameter and bead numbers (determined by scanning electron microscopy images) and an increase in the crystallinity (confirmed by X‐ray diffraction patterns). A continuous rate of silver release from the nanofiber web was monitored by the atomic absorption technique. These nanofibers showed strong antibacterial activity against Pseudomonas aeruginosa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Size Effect of 3D Aggregates Assembled from Silver Nanoparticles on Surface‐Enhanced Raman Scattering

The size influence of 3D silver nanoparticle aggregates on surface-enhanced Raman scattering (SERS) is investigated. Micrometer- and nanometer-sized wells prepared on a polydimethylsiloxane (PDMS) surfaces are filled with cetyltrimethylammonium bromide (CTAB)-coated silver nanoparticles. A concentration of CTAB around its critical micelle concentration is used not only to form a bilayerlike structure around the nanoparticles and thus generate nanometer-sized gaps in the aggregates, but also to improve the compatibility of the surface charge properties of the silver nanoparticles with the surface of PDMS and thus successfully fill the wells by assembly of silver nanoparticles into 3D structures. A resonance-free enhancement factor of 10(7) can be easily achieved on larger aggregates, and the enhancement factor increases with decreasing size of the 3D aggregates, which is contrary to reported studies on conventional silver clusters. We find that the number of silver nanoparticles in the 3D aggregate should be less than 200-300 for optimal SERS performance.

Convenient Synthesis and Characterization of Silver/Poly(p-Cl-phenylsilane) Nanocomposites

The one-pot preparation and structural characterization of silver/poly(p-Cl-phenylsilane) nanocomposites have been performed. The one-step transformation of silver(I) salt to stable silver(0) nanoparticles is mediated by poly(p-Cl-phenylsilane), Cl-PPS having both reactive Si-H bonds in the polymer backbone and C-Cl bonds in the substituents. XRD, TEM, and FE-SEM, and solid-state UV-vis analytical techniques were used to analyze the interesting metal/inorganic polymer hybrid nanocomposites. TEM and FE-SEM data show the formation of hybrid composites in which large number of silver nanoparticles (less than 30 nm of size) are dispersed throughout the Cl-PPS matrix. XRD patterns are consistent with that for fcc-typed silver. The elemental analysis for Cl atom and the polymer solubility confirm that the appreciable cleavage of C-Cl bond and the Si-Cl dative bonding were not occurred. The size and processability of such nanoparticles depend on the ratio of metal to Cl-PPS. In the absence of Cl-PPS, most of the silver particles undergo macroscopic aggregation, which indicates that the polysilane is absolutely necessary for stabilizing the silver nanoparticles.

Preparation and Characterization of Silver Nanoparticles in the Presence of Inclusion Complex of β-Cyclodextrin with Phenylsilane

Silver nanoparticles are prepared in an aqueous medium consisting of an inclusion complex beta-CD/PS, formed between beta-cyclodextrin (beta-CD) and phenylsilane (PS). The PS acts as a reducing agent. beta-CD/PS complex stabilizes the Ag nanoparticles preventing agglomeration and provides a self-assembling environment for forming nanostructure around Ag nanoparticles. The TEM (transmission electron microscopy) and FE-SEM (field emission scanning electron microscopy) data suggest the formation of hybrid composites in which large numbers of silver nanoparticles (< 20 nm) are dispersed. SAED patterns are consistent with that for fcc-typed silver. In the absence of the beta-CD/PS inclusion complex, most of the silver particles underwent macroscopic precipitation, which indicates that the beta-CD/PS inclusion complex is essential for stabilizing the silver nanoparticles.