Source Of Silver Ions Research Articles

Staircase and pulse potential electrochemical techniques for the facile and rapid synthesis of Pt and PtAg materials

Electrochemical synthesis is an attractive option for the synthesis of materials because electrocrystallization is faster (microseconds), easier (fewer variables influence structure) and more cost-effective (only requiring an ion source and electrolyte) than traditional chemical methods. Pt and PtAg materials were synthesised using electrochemical techniques, including staircase cyclic voltammetry (CV). Differential pulse amperometry (DPA), square wave voltammetry (SWV) and second harmonic AC voltammetry (2nd H AC V) were employed as pulse potential techniques. Characterisation was conducted using X-ray diffraction, field emission scanning electron microscopy, X-ray fluorescence, cyclic voltammetry in acidic and basic media and by assessing the behaviour of the synthesised materials in oxygen reduction reaction (ORR). For the cyclic voltammetry and DPA techniques, a decrease in the interfacial electrode/solution concentration resulted in the formation of semi-spherical nanoparticles with dendritic nanosheet growth. Semi-spherical Pt nanoparticles with small crystal sizes were obtained using SWV and 2nd H AC V due to the enhancement of the Pt seed growth by the low-time pulse potential period. Silver incorporation allowed the formation of well-defined cubic-shaped and flower-like PtAg nanoparticles without the need for surfactants and/or reductants. Silver acted both as a silver ion source and an additive, due to its passivation of the particle surfaces.

Nano-Silver Mediated Polymerization of Pyrrole: Synthesis and Gas Sensing Properties of Polypyrrole (PPy)/Ag Nano-Composite

Thermal polymerization of pyrrole was performed using silver nitrate as source of silver ions followed by its conversion to Polypyrrole (PPy)/Ag nano-comoposites without using any external oxidizing agent or solvent. The formation of PPy was monitored by UV-Visible absorption spectroscopy showing a band at approximately 464 nm. XRD measurement confirmed characteristic peaks for face centered cubic (fcc) silver and presence of PPy at 2 theta of approximately 23 degrees suggesting the formation of PPy/Ag nanocomposite. Transmission electron microscopy (TEM) images showed non-aggregated spherical Ag nano-particles of about 5-10 nm. PPy/Ag thick film acts as a NH3 sensor at 100 degrees C, a H2S sensor at 250 degrees C and CO2 sensor at 350 degrees C. The thick films showed capability to recognize various gases at different operating temperature.

Preparation and properties of silver nanoparticles loaded in activated carbon for biological and environmental applications

Abstract Silver nanoparticles colloid has been prepared by a modified sonoelectrodeposition technique in which a silver plate was used as the source of silver ions. This technique allows producing Ag nanoparticles with the size of 4–30 nm dispersed in a non-toxic solution. The Ag nanoparticles were loaded in a high surface activated carbon produced from coconut husk, a popular agricultural waste in Vietnam by thermal activation. The surface area of the best activated carbon is 890 m 2/g. The presence of Ag nanoparticles does not change significantly properties of the activated carbon in terms of morphology and methylene blue adsorption ability. The Ag nanoparticle-loaded activated carbon shows a good antibacterial activity against Escherichia coli with very low minimal inhibitory concentration of 16 μg/ml and strong As(V) adsorption. The materials are potential for prevention and treatment of microbial infection and contamination for environmental applications.

Silver nanoparticles induce oxidative cell damage in human liver cells through inhibition of reduced glutathione and induction of mitochondria-involved apoptosis

Silver nanoparticles (AgNPs), which have well-known antimicrobial properties, are extensively used in various medical and general applications. Despite the widespread use of AgNPs, relatively few studies have been undertaken to determine the cytotoxic effects of AgNPs exposure. This study investigates possible molecular mechanisms underlying the cytotoxic effects of AgNPs. Here, we show that AgNPs-induced cytotoxicity was higher compared than that observed when AgNO 3 was used as a silver ion source. AgNPs induced reactive oxygen species (ROS) generation and suppression of reduced glutathione (GSH) in human Chang liver cells. ROS generated by AgNPs resulted in damage to various cellular components, DNA breaks, lipid membrane peroxidation, and protein carbonylation. Upon AgNPs exposure, cell viability decreased due to apoptosis, as demonstrated by the formation of apoptotic bodies, sub-G 1 hypodiploid cells, and DNA fragmentation. AgNPs induced a mitochondria-dependent apoptotic pathway via modulation of Bax and Bcl-2 expressions, resulting in the disruption of mitochondrial membrane potential (Δ ψ m). Loss of Δ ψ m was followed by cytochrome c release from the mitochondria, resulting in the activation of caspases 9 and 3. The apoptotic effect of AgNPs was exerted via the activation of c-Jun NH 2-terminal kinase (JNK) and was abrogated by the JNK-specific inhibitor, SP600125 and siRNA targeting JNK. In summary, the results suggest that AgNPs cause cytotoxicity by oxidative stress-induced apoptosis and damage to cellular components.

Cytotoxic effect and apoptosis induction by silver nanoparticles in HeLa cells

Nanosilver has well-known antibacterial properties, and is widely used in daily life as various medical and general products. In comparison with silver ion, there is serious lacking of information concerning the biological effects of nanoAg. In this study, we observed the cytotoxic effect of nanoAg in HeLa cells. The nanoAg-induced cytotoxicity was lower than that of AgNO 3, used as a silver ion source. Apoptosis evaluated by flowcytometric analysis was associated with this cell death. Further, the expressions of ho-1 and mt-2A, well-known oxidative stress-related genes, were up-regulated by nanoAg treatment. Our results showed that nanoAg possesses the potential for cytotoxicity, therefore, in the case of exposure at high concentrations, we should consider to protect from nanoAg-induced toxicity.

Development of a silver ion source using nanosecond pulses of a Nd:YAG laser at different wavelengths

A silver ion source was designed by focusing the fundamental and harmonics of Q-switched Nd:YAG laser pulses onto a silver target and simultaneously applying an electric potential in an argon environment. The silver ions were detected at a distance of 2 cm from the target surface using a Faraday cup ion probe after letting them pass through a retarding mesh grid (copper electrode). We aim to produce and characterize the silver ions generated by the laser radiation of different wavelengths and pulse energy, ambient gas pressure and the electrode spacing under applied electric field. In addition to this, the effect of laser radiation on plasma under vacuum and at different argon gas pressures was investigated. The velocity distribution function of the plasma emitted from the silver target was investigated under argon discharge. These measurements demonstrated clearly that the velocity distribution function and current signals depend on laser power, laser wavelength and argon pressure. We observed a ten fold increase in the plume current with increase in the applied voltage and ion velocity in the presence of a laser field. The surface morphology of the laser irradiated samples was investigated using reflection optical microscopy.

Rapid, Facile Synthesis of Silver Nanostructure Using Hydrolyzable Tannin

A facial and distinct synthesis process of silver nanoparticles stabilized by tannin in aqueous medium is reported. Silver nitrate is solubilized in water as the source of silver ions, and tannin is solubilized in water as both a reducing agent and stabilizer matter. Due to hydroxyl groups and the dendritic macrostructure of tannin, it was used as both a reducer and stabilizer. The concentrations of tannin and of AgNO3 solution were changed to observe variation in particle size. However the role of the dendritic tannin molecule in forming silver nanoparticles was explained, and changes of the tannin molecule due to the redox reaction were determined by Fourier transform infrared (FTIR) measurements. The structure of synthesized silver nanoparticles has been investigated through scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis revealed the face-centered cubic (fcc) geometry of silver nanoparticles. Also a UV−vis spectrophotometer was used to obtain the absorption spectrum of silver nanoparticles.

Formation of silver nanoparticles in SDS inverse microemulsions

Silver nanoparticles have been synthesized using silver nitrate solubilized in the water core of one microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another microemulsion as reducing agent, cyclohexane as the continuous phase, sodium dodecyl sulfate (SDS) as the surfactant, and isoamylalcohol as the cosurfactant. The effects of AgNO 3 concentration and the molar ratios of water to SDS ( W) on the particle size and size distribution are investigated. UV–vis spectra show that the Ag 4 + intermediates formed at early stages of the reaction and then the clusters grow and formed into larger nanoparticles. TEM micrographs confirm that the silver nanoparticles are spherical. Their mean diameters increase from 6.5 nm to 12.1 nm with W values, and the size distribution also increases obviously with the W values. By absorption of SDS molecules from microemulsions, the as-prepared nanoparticles are stable without aggregation. However, the stabilization achieved by absorption of SDS, i.e., the protection of Ag nanoparticles by SDS, is relatively weak.

Synthesis of nanosilver colloidal particles in water/oil microemulsion

Colloidal silver nanoparticles have been synthesized using silver nitrate solubilized in the water core of one microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another microemulsion as reducing agent, dodecane as the oil phase and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The effect of AgNO 3 concentration and the molar ratios of water to AOT ( W) in microemulsion on the particle size, the size distribution and the stabilization have been investigated. Transmission electron microscopy (TEM) results show that the silver nanoparticles are all spherical and have a narrow size distribution as well as a good stability. The higher the AgNO 3 concentration, the faster the growth rate of the silver particles. The higher W value has been found to give larger particle size and broader size distribution. The resultant nanosilver colloid has low toxicity and high stabilization. As a result, the colloidal nanoparticles need not be separated from the solution and the silver sol can be directly used in antibacterial fields.

Synthesis and characterization of silver nanoparticles in AOT microemulsion system

Colloidal silver nanoparticles have been synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of one microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another microemulsion as reducing agent, dodecane as the oil phase, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The UV–vis absorption spectra and transmission electron microscopy (TEM) have been used to trace the growth process and elucidate the structure of the silver nanoparticles. UV–vis spectra show that the Ag 4 + intermediates formed at early stages of the reaction and then the clusters grow or aggregate to larger nanoparticles. TEM micrographs confirm that the silver nanoparticles are all spherical. The resulting particles have a very narrow size distribution. Meanwhile, the diameter size of the particles is so small that the smallest mean diameter is only 1.6 nm. IR results show that the surfactant molecules are strongly adsorbed on the surface of silver particles through a coordination bond between the silver atom and the sulfonic group of AOT molecules, which endows the particles with a good stability in oil solvents. As dodecane is used as oil solvent to prepare silver nanoparticles, the formed nano-silver sol is almost nontoxic. As a result, the silver nanoparticles need not be separated from the reaction solution and the silver sol may be directly used in antibacterial fields.

Characterization of the Phase and Structure of Interfaces Formed During the Synthesis of Silver Halide-Silver Carboxylate Compositions

In the preparation of the AgX/[AgO2CR]2 components that are used in photothermographic imaging films, where X = Br or Cl and R = linear alkyl chain, the reaction of silver ions with sodium fatty acid salts produces various silver soap structures containing different interface properties, depending on the starting silver ion source. Use of pre-prepared silver bromide microcrystals and silver nitrate, for example, has been shown to produce a AgBr/[AgO2CR]2 epitaxial interface. Conversely, we now find that silver chloride can be reacted directly with NaO2CR to prepare a [Ag(O2CnH2n−1)]2 product without needing to add silver nitrate. In this article we report the results of our continuing investigation, by TEM and X-ray diffraction, of the nature of the interface formed between prepared silver halides and [AgO2CR]2.

Electrochemical Properties of Silver‐Nylon Fabrics

Composites consisting of inert fiber substrates coated with metallic silver were shown to be potentially useful as a source of silver ions for infection control. Using an in vitro system, the ability of six silver‐coated nylon fabrics to support an electric current was studied, and the resulting silver levels up to 23h after initiation of the current were measured. In four fabrics, 1.7 μA/cm2 for 16h produced fabric corrosion that prevented further current flow. Comparable changes in two other fabrics did not occur until 16 μA/cm2. At fixed current densities, the fabrics produced differing solution silver concentrations. For one fabric, the measured silver concentrations approached the theoretically predicted level. The results indicated that silver‐nylon fabrics could produce antimicrobially significant silver levels at relatively low currents and voltages, and that the rate of ion production can be predicted on the basis of electrochemical considerations.

The reduction of silver salts by htdroxylamine

In the pH range of 4–6 the reduction of silver(I) salts by hydroxylamine is autocatalytic and yields metallic silver and nitrogen. The rate of reduction is directly related to the area of metal surface and to the concentration of the complex ion, Ag(NH 2OH) +, present in solution. The induction period in the reaction can be eliminated by pre-addition of silver particles or by using silver oxide as the source of silver ions.