Amount Of Silver Nanoparticles Research Articles

The effect of carrier salts blending on the morphology, stability and permeation properties of PES/PEO facilitated transport membranes

In this research, mixtures of Cu(NO3)2 and AgBF4 salts were used in preparation of poly(ethersulfone) (PES)/poly(ethylene oxide) (PEO) composite facilitated transport membranes. Reduction of carrier agent is known as the main challenge for this type of membranes. The effect of salt blending on the reduction behavior of silver carrier sites was analyzed through permeation and structural properties of composite membranes. Based on UV–Visible, mixed and ideal permeation experiments, the existence of copper divalent cations beside silver monovalent cations will result in delay in reduction time of silver cations. Therefore, the membrane selectivity is retained at higher values. However, starting selectivity of membranes containing silver salt ions (case 2) with concentration above threshold level is higher than other membranes containing both salts (case 1). TEM analysis proved that size and quantity of silver nanoparticles in the membranes of case 1 are less than membranes of case 2. Applying copper salt increased the potential of ions aggregated distribution in membranes structure according to FTIR–ATR analysis. Aggregation is one of the reasons for less initial separation potency in comparison with membranes without copper salt. Incorporation of cooper salt enhanced the surface roughness and mechanical strength of initial membranes containing silver salt alone.

Sensitive Quantification of Silver Nanoparticles by Kinetic-Spectrophotometry Method in Groundwater Samples

A novel kinetic-spectrophotometry method is developed for the determination of trace amounts of silver nanoparticles (AgNPs) in groundwater samples based on their catalytic effect on the oxidation of indigo carmine by hexacyanoferrate (III) in acetate-acetic acid medium. The absorbance was measured at 612 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents and interferences was investigated. The calibration curve is linear over the concentration range 4.0–300 μg mL−1 of AgNPs with good precision and accuracy. The proposed method is a highly sensitive, selective, and relatively rapid assay of AgNPs at trace level. The method was applied to the determination of AgNPs in groundwater and a synthetic sample.

Realization and Characterization of POLICRYPS-like Structures Including Metallic Subentities

A first characterization of newly realized micro periodic structures including metallic nanoparticles is reported. The original mixture, generally utilized for the realization of polymer-liquid-crystal-polymer-slices gratings (POLICRYPS), has been enriched with a small amount of silver nanoparticles. The obtained structure shows a spectral response that strongly depends on the polarization of the probing light. These first structures are oriented to the fabrication of devices with metamaterial properties.

Remarkable fluorescence enhancement in YVO4:Eu3+@Ag nano-hybrids induced by interface effect

The luminescence enhancement effect induced by the coupling of noble metal nanoparticles (NPs) with rare earth (RE) doped nanophosphors is attracting current interests. In order to obtain efficient luminescence enhancement and clarify its physical nature, the YVO4:Eu3+@Ag core-shell nano-hybrids colloids were first prepared by a facile two-step seed-mediated growth method. The luminescence enhancement of 5D0–7FJ transition for Eu3+ with a maximal factor of ∼one order was observed, which strongly depended on the amount of silver NPs, the concentration of the YVO4:Eu3+ colloids and the dissolved solutions. The enhancement mechanism was carefully discussed based on absorption spectra, emission spectra, luminescent decay dynamics and zeta potentials of colloids solutions. The results indicate that the silver NPs on the surface of YVO4:Eu3+ can effectively prevent VO43− and Eu3+ from the interaction with the solvent such as OH bonds, leading to a decrease of nonradiative energy transfer (ET) and suppressed luminescent quenching. A detailed model was proposed to explain the interesting luminescence enhancement behavior.

Preparation of poly(vinylidene fluoride)-silver nanoparticle composite using dimethylformide as both a solvent and a reductant

AbstractPoly(vinylidene fluoride)-silver nanoparticle (PVDF-Ag) composites were synthesized by in situ reduction of silver salt using dimethylformide (DMF) as both a solvent and a reductant. The crystalline properties (e.g., crystallinity and the types of crystals) of the composites were characterized. It was shown that PVDF in the composites had a higher melting temperature than pure PVDF, and the α phase crystal in the composites became more stable with an increase in the amount of silver nanoparticles. The mechanical properties and morphologies of the composites were also investigated. It was noted that the PVDF-Ag composites have better mechanical properties when silver nanoparticles were added. The increase in toughness could be attributed to the formation of continuous structure between PVDF and silver particles.

Synthesis of silver nanoparticles using dl-alanine for ESR dosimetry applications

The potential use of alanine for the production of nanoparticles is presented here for the first time. Silver nanoparticles were synthesized using a simple green method, namely the thermal treatment of silver nitrate aqueous solutions with dl-alanine. The latter compound was employed both as a reducing and a capping agent. Particles with average size equal to 7.5 nm, face-centered cubic crystalline structure, narrow size distribution, and spherical shape were obtained. Interaction between the silver ions present on the surface of the nanoparticles and the amine group of the dl-alanine molecule seems to be responsible for reduction of the silver ions and for the stability of the colloid. The bio-hybrid nano-composite was used as an ESR dosimeter. The amount of silver nanoparticles in the nanocomposite was not sufficient to cause considerable loss of tissue equivalency. Moreover, the samples containing nanoparticles presented increased sensitivity and reduced energetic dependence as compared with pure dl-alanine, contributing to the construction of small-sized dosimeters.

In situ deposition of silver nanoparticles on the cotton fabrics

A novel method was developed to prepare the antibacterial cotton fabrics through in situ deposition of silver nanoparticles on the cotton fabrics by the reduction of Ag+ without any reductant and dispersant. The data showed that by immersing the cotton fabrics in 160 mM AgNO3 solution at 90 °C, the amount of silver nanoparticles was increased from 0.6890 to 1.3561 mg per gram of fabrics with the increase of reaction time from 10 to 50 min. The obtained cotton fabrics showed excellent antibacterial activity and laundering durability, in which the bacterial reduction was still 98.5 and 94.3 % to Escherichia coli and Staphylococcus aureus, respectively, even after the fabrics were washed for 20 cycles. Thus, this facile in stitu reduction method without any other reducers or stabilizers may bring a promising and green strategy to produce functional cotton fabrics.

Effect of Nano Sized Silver on Electrospun Nylon-6 Fiber

We incorporated silver nanoparticles into a nylon solution, fabricated electrospun nanofibers, and studied various parameters of the electrospun fibers. We found that the addition of silver nanoparticles introduces antibacterial effects into nylon composite fibers. The average fiber diameter and fiber morphology was greatly affected when parameters such as solution concentration and the amount of silver nanoparticles were changed. The composite fibers that we prepared have the potential to be used as filtration membranes.

Antibacterial activity of pH-sensitive genipin cross-linked chitosan/poly(ethylene glycol)/silver nanocomposites

Novel nanocomposites consisting of genipin cross-linked chitosan (GC), poly(ethylene glycol) (PEG), and silver nanoparticles were prepared for such biomedical applications as the wound-healing materials. Various amounts of silver nanoparticles were dispersed in the GC/PEG hydrogel matrix without severe aggregation. The effects of composition and silver nanoparticles on the physico-chemical properties of samples were evaluated by infrared analysis, contact angle measurements, and swelling tests. The GC/PEG/Ag nanocomposite showed a pH-sensitive swelling behavior. The surface hydrophilicity of GC/PEG/Ag nanocomposites was improved with the increase of silver nanoparticle content. L929 cell attachment was improved in the presence of silver nanoparticles. The antimicrobial function was assessed for the GC/PEG/Ag nanocomposites containing the silver content over 100 ppm. The silver nanoparticles had the dual functions of reinforcing structural stability and enhancing antimicrobial activity of GC/PEG/Ag nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.

Self-assembled chitosan/heparin multilayer film as a novel template for in situ synthesis of silver nanoparticles

Chitosan and heparin multilayer films were successfully constructed via layer-by-layer self assembly. These films were used as a polymeric template to synthesize silver nanoparticles. The silver concentration and nanoparticle size can be simply controlled by the assembly pH and loading pH, as demonstrated by UV-visible spectroscopy, transmission electron microscopy and atomic absorbance spectroscopy. The pH tunable uncompensated charge density within the multilayer films is believed to have great effect on the loading of silver ions, and then control the size and amount of silver nanoparticles within multilayer films. The antibacterial experiment shows that the silver nanoparticle-loaded chitosan/heparin multilayer films exhibit greatly enhanced antibacterial performance compared to the chitosan/heparin multilayer films without silver nanoparticles. In addition, the strong antibacterial property of silver nanoparticle-loaded films can last more than 1 month. Our method of in situ synthesis of metal nanoparticles in biocompatible multilayer films might provide great potential to design biofunctional nanocomposite films.

Application of Gradient and Confocal Raman Spectroscopy to Analyze Silver Nanoparticle Diffusion in Medieval Glasses

In this work it has been carried out the diffusion of silver ions in medieval glasses by a heat treatment process. Silver ions are transformed into both silver nanoparticles and nanoclusters after redox reactions with reducing glass ions. Changes in glass colour due to the formation of these silver nanoparticles have been analysed by means of visible spectroscopy. At the same time, changes in glass structure have been analysed by means of Raman scattering. By using confocal Raman spectroscopy the in deep glass structural changes occurring after silver ion diffusion and silver nanoparticle formation have been studied. These changes have been corroborated by means of gradient Raman spectroscopy where the silver ion and silver nanoparticle diffusion have been analysed on a fractured glass surface. In all cases have been observed that silver nanoparticles produce a depolymerisation of the glass structure and that such depolymerisation increases with the amount of silver nanoparticles. By using Microprobe Analysis it has been found that the higher silver nanoparticle concentration is on the glass surface and it decreases with the distance to the surface according to a diffusion process. By using nanoindentation measurements on original and gradient glass surfaces it has been found an increase of the Young modulus from 60 to 85 GPa, being the first value that corresponding to the glass surface with high silver nanoparticle concentration, and the second one for the glass without silver. This result is in accordance with Raman and Microprobe analysis.

Luminescence of Tb3+ doped TeO2–ZnO–Na2O–PbO glasses containing silver nanoparticles

Luminescence properties of Tb3+ doped TeO2–ZnO–Na2O–PbO glasses containing silver nanoparticles (NPs) were investigated. The absorption band due to the surface plasmon resonance in the NPs was observed. Its amplitude increases with the heat treatment of the samples that controls the nucleation of the NPs. Tb3+ emission bands centered at ≈485, ≈550, ≈585, and ≈623 nm were detected for excitation at 377 nm. The whole spectrum is intensified by the appropriate annealing time of the samples. Enhancement by ≈200% of the Tb3+ luminescence at 550 nm was observed for samples annealed at 270 °C during 62 h. This enhancement effect is due to the local field amplitude that increases with the amount of silver NPs and their aggregates.

Morphological analysis of self-assembled SIS block copolymer matrices containing silver nanoparticles

The intrinsic ability of block copolymers to self-assemble at nanoordered level into different nanoscale structures has been used in this study to obtain nanocomposites. Ordered architectures of silver nanoparticles confined in a poly(styrene- b-isoprene- b-styrene) (SIS) block copolymer matrix have been generated. Both cetyl trimethylammonium chloride (TMAC) and dodecanethiol (DT) were used as surfactants to obtain dispersed nanocomposite films. Morphologies generated in Ag/SIS nanocomposites, detected through atomic force, resulted to be more dependent on the amount of silver nanoparticles than on the other variables chosen in the present study such as amount and type of surfactant and preparation parameters. The experimental observations are consistent with phase diagram predictions obtained for hybrid systems composed of block copolymers and nanoparticles.

A versatile strategy to fabricate hydrogel–silver nanocomposites and investigation of their antimicrobial activity

In this study, hydrogel–silver nanocomposites have been synthesized by a unique methodology, which involves formation of silver nanoparticles within swollen poly (acrylamide- co-acrylic acid) hydrogels. The formation of silver nanoparticles was confirmed by transmission electron microscopy (TEM) and surface plasmon resonance (SPR) which was obtained at 406 nm. The TEM of hydrogel–silver nanocomposites showed almost uniform distribution of nanoparticles throughout the gel networks. Most of the particles, as revealed from the particle-size distribution curve, were 24–30 nm in size. The X-ray diffraction pattern also confirmed the face centered cubic (fcc) structure of silver nanoparticles. The nanocomposites demonstrated excellent antibacterial effects on Escherichia coli (E. coli). The antibacterial activity depended on size of the nanocomposites, amount of silver nanoparticles, and amount of monomer acid present within the hydrogel–silver nanocomposites. It was also found that immersion of plain hydrogel in 20 mg/30 ml AgNO 3 solution yielded nanocomparticle–hydrogel composites with optimum bactericidal activity.