Aqueous Dispersions Of Silver Nanoparticles Research Articles

Comparative Analysis of Stable Aqueous Dispersion of Silver Nanoparticle Synthesized from Mangifera Indica and Azadirachta Indica Leaf Extract

Mango and neem leaf extract were prepared by soaking the measured leaves into 100ml of distilled water under appropriate conditions. Consequently, biosynthesis of silver nanoparticles was carried out by distinctly adding the mango and neem leaf extract to prepared solution of silver nitrate (AgNO3) to produce aqueous dispersion of silver nanoparticles. The silver nanoparticles produced were investigated using FTIR, UV-Visible and AFM Spectroscopy at 15 minutes, 24 hours and 48 hours respectively. Reduction in OH absorption proves chemical interaction of mango extract with AgNO3. UV/Visible also revealed colour changes from faint yellow to brown to reddish brown within 15 minutes and 24 hours of incubation at room temperature. Atomic Force Microscopy revealed that the sizes of mango-based dispersion are smaller than that of neem-based dispersion.

Antimicrobial activity of aqueous dispersions of silver nanoparticles against pathogens of purulent-inflammatory diseases

Currently, metal nanostructures are widely used in medical, microbiological, and veterinary practice. Silver nanoparticles are especially promising as antimicrobial agents, becauseno published data regarding antimicrobial resistance are available. Whiledeveloping preparations based on metal nanoparticles, an important remainingissue is the choice of a stabilizer, introduction of which during the synthesis ensures the preservation of structures at the nanoscale range, and, consequently, relevant main characteristics, including biocidal properties. The object of the study was to investigate silver nanoparticle aqueous dispersions stabilized by natural and synthetic polymeric compounds. Routine strains of Gram-positive and Gram-negative bacteria were used as experimental models: S. aureus 209 P, Escherichia coli ATCC 25922, Proteus mirabilis ATCC 3177 (O-form), Klebsiella pneumoniae ATCC 31488, obtained from the Scientific Centre for Expert Evaluation of Medicinal Products. The antimicrobial activity of diverse variants of silver nanoparticle aqueous dispersions was assessed by serial dilution platingon dense nutrient medium. In this work, we examined no effect of silver nanoparticles without stabilizers, because their absence led to rapid agglomeration of nanostructures and loss of nanoscale characteristics. The highest sensitivity of Gram-positive and Gram-negative bacteria was foundto the action of ansilver nanoparticle aqueous dispersions stabilized by polyazolidinammoniumand modified with iodine hydrate ions. Drug working concentrations ranging from 0.5 to 3% had a bactericidal effect against pathogens of purulent-inflammatory diseases, and the minimum working concentration of 0.125% led to decreased colony-forming units by 2057% for diverse bacterial strains. Silver nanoparticles stabilized with sodium dodecyl sulfate showed high efficiency against the studied test strainsprobably due to the high toxicity of the stabilizer used as was previously established during a comprehensive safety assessment using biotest objects and cell cultures. In this regard, its use as a component of antimicrobial preparations is not preferred. The results of the studies showed that among the variants of silver nanoparticle aqueous dispersions, preparations stabilized with polyvinyl alcohol and polyazolidinammonium modified with iodine hydrate ions are the most promising for use in biomedical practice, because they demonstrate a high level of antibacterial activity against both Gram-positive and Gram-negative bacteria as causative agents of purulent-inflammatory diseases and a low toxicity level. This allows us to recommend them as safe and effective antimicrobial components indisinfectants, as well as antiseptic preparations for prevention and treatment of skin and soft tissue infectious diseases.

Biosynthesis of silver nanoparticles using nanocurcumin extracted from fresh turmeric of Vietnam

Abstract This study presents a novel process to synthesize curcumin nanoparticles from fresh turmeric. An ultrasonic-assisted cajeput oil in water emulsion technique was used to synthesize nanocurcumin. The prepared nanocurcumin was spherical with an average size of 47 nm and size distribution of 5–80 nm. The synthesized nanocurcumin showed improved aqueous-phase solubility, and it was used as a reducing agent and stabilizer for biosynthesizing silver nanoparticles. Furthermore, the X-ray diffraction pattern of the silver nanoparticles showed four distinct diffraction peaks at 38.3°, 44.6°, 65.1°, and 78.1° corresponding to the lattice planes of face-centered cubic silver ((111), (200), (220), and (311)). Transmission electron microscopy analysis indicated the average size and maximum size distribution (80 %) of the silver nanoparticles were 10.9 nm and 5–15 nm, respectively. UV–visible spectroscopy measurement of samples indicated the localized surface plasmon resonance absorbance of an aqueous dispersion of silver nanoparticles at 406 nm. Zeta potential analysis revealed a negative charge with a magnitude of −27.2 mV, which indicated higher aqueous dispersion stability of the silver nanoparticles prepared from nanocurcumin. The nanoparticles showed antibacterial activity against Vibrio parahaemolyticus.

Effect of Foliar Treatment with Aqueous Dispersions of Silver Nanoparticles on Legume-Rhizobium Symbiosis and Yield of Soybean (Glycine max L. Merr.)

Interest in the use of silver as a component of plant protection products and growth regulators appeared relatively recently with the development of methods for the effective stabilization of colloidal systems containing nanoparticles of this metal. In the present work, we studied the effect of foliar treatments with aqueous dispersions of silver nanoparticles stabilized by polyhexamethylene biguanide hydrochloride with an average diameter of 6 ± 1 nm and a zeta-potential of +47.4 ± 1.3 mV on legume-Rhizobium symbiosis, which largely determines the efficiency of soil nitrogen assimilation and the yield of soybean (Glycine max L. Merr.). Based on the results of a two-year field experiment, it was shown that treatments with low doses of silver nanoparticles lead to a significant increase in the number of root nodules and an increase in soybean yield. The observed biological effectiveness of silver nanoparticles dispersions is explained by an increase in the enzymatic activity of peroxidases and polyphenol oxidases in the terrestrial part of plants. It is very likely that the treatment with silver nanoparticles and the increase in peroxidase activity in non-infected parts of the plant lead to a more effective prevention of the penetration of rhizobacteria into the aboveground soybean organs, which, in turn, may be the reason for the observed decrease in the activity of peroxidase and polyphenol oxidase in parts of plant roots susceptible to rhizobia. The latter, as is known, contributes to an easier flow of the nodulation process and the development of legume–Rhizobium symbiosis.

Surface-enhanced Raman scattering of water in aqueous dispersions of silver nanoparticles.

The resonance Raman effect (RRE) is a phenomenon which results in a strong selective enhancement of Raman signals from the samples. Previous studies showed that the RRE in liquid water directly corresponds to its supramolecular structure. It was also reported that the electric-field-induced orientation of water molecules on the electrode surface results in the surface-enhanced Raman scattering (SERS) effect. In this work, we show the SERS effect for water molecules in the dispersion of silver nanoparticles (AgNPs) without any external electrical field. An enhancement factor was estimated to be (4.8 ± 0.8) × 106 for an excitation wavelength of 514.5 nm and for AgNPs with an average size of 34 ± 14 nm. The temperature experiment results showed a higher enhancement with temperature increase. Performed simulation studies revealed a slowdown of the mobility of the water molecules close to the surface of AgNPs.

Spontaneous versus Stimulated Surface-Enhanced Raman Scattering of Liquid Water.

We have observed for the first time the surface-enhanced (SE) signal of water in an aqueous dispersion of silver nanoparticles in spontaneous (SERS) and femtosecond stimulated Raman (SE-FSRS) processes with different wavelengths of the Raman pump (515, 715, and 755 nm). By estimating the fraction of water molecules that interact with the metal surface, we have calculated enhancement factors (EF): 4.8 × 106 for SERS and (3.6–3.7) × 106 for SE-FSRS. Furthermore, we have tested the role of simultaneous plasmon resonance and Raman resonance conditions for the aν1 + bν3 overtone mode of water (755 nm) in SE-FSRS signal amplification. When the wavelength of the Raman pump is within the plasmon resonance of the metal nanoparticles, the Raman resonance has a negligible effect on the EF. However, the Raman resonance with the aν1 + bν3 mode strongly enhances the signal of the fundamental OH stretching mode of water.

Physicochemical Characterization of Polyvinyl Pyrrolidone: A Tale of Two Polyvinyl Pyrrolidones.

Of several samples of polyvinyl pyrrolidone (PVP) used to coat and stabilize freshly manufactured aqueous dispersions of silver nanoparticles, one batch gave anomalous results: the dispersion maintained continued stability, even on extensive dilution. Our efforts to understand this desirable feature concluded that the generally used spectral method of PVP purity verification, Fourier transform infrared (FTIR) spectroscopy, was incapable of answering our inquiry. This led to the employment of several other methods, including X-ray photoelectron and nuclear magnetic resonance spectroscopies, which ultimately revealed several possible reasons for the dilution stability, including incomplete PVP hydrolysis during manufacture and the presence of hydroperoxide contaminants. It led, as well, to explanations for the shortcomings of FTIR spectroscopy as a verification method for PVP purity.

Effect of silver nanoparticles on the solubility of methane and ethane in water

In this work, the solubility of methane and ethane were studied in aqueous dispersion of silver nanoparticles (1, 5, and 10 ppm) at temperatures of 1, 2.5, 10, and 11.5 °C for methane and 2.5, 5, 10, 15.5 °C for ethane and at initial pressures 1 to 5.5 and 0.35–2.15 MPa for methane and ethane, respectively. The nanoparticles were synthesized and characterized through UV–vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM) image. The results demonstrated that silver nanoparticles increased the solubility of methane and ethane up to 13 and 16% compared with pure water, respectively. The solubility of methane and ethane were enhanced by increasing the nanoparticles mass loading. The effect of nanoparticles on ethane solubility was more significant than methane solubility.

Determination of silver in tissues and organs of broiler chickens after oral and aerosol administration of an aqueous dispersion of silver nanoparticles

An aqueous dispersions of silver nanoparticles (10 ppm, 50 ppm, 300 ppm) stabilized with 100-600 ppm of chloride benzyldimethyl[3-(myristoylamino)propyl]ammonium monohydrate (miramistin) have been used in the experiment. These compositions were registered in Russia in 2014 as a veterinary drug under the brand name Argumistin®. One of the indications for oral and aerosol administration of Argumistin® is respiratory and gastrointestinal infections of broiler chickens. Miramistin-stabilized silver nanoparticles administered at a dose of 0.32 pg of silver per 1 kg of body weight per day almost completely retained in the body of broilers, while the increasing of the administered dose up to 1.92 pg of silver per 1 kg of body weight per day reduced the retention rate up to 30%. With taking into account WHO recommendations and Russian regulations the oral administration of 10 ppm of silver at above mentioned doses can be concluded to fail to cause accumulation of silver in the tissue and organs of broiler chickens in concentrations dangerous for humans.

Piezoelectric Inkjet-Printed Metallic Igniters

This work demonstrated printed metallic bridge wire and spark gap igniters suitable for use with energetic materials. These devices were fabricated from an aqueous dispersion of silver nanoparticles on a flexible, mesoporous substrate using a piezoelectric inkjet printer. This manufacturing process resulted in precise samples fabricated without the need for thermal curing. Geometric parameters were varied for the devices to determine the design criteria of importance and to quantify the electrical excitation needed for optimal performance. The work successfully demonstrated the integration of bridge wires and spark gaps with energetic material to produce fully printed igniters that are of practical use in applications ranging from munitions to vehicle airbags.

Nucleation of ethane hydrate in water containing silver nanoparticles

Since, nucleation aspects of hydrate formation are important, experimental and theoretical description of hydrate nucleation in the presence of triangular silver nanoparticles were evaluated. In this work, the induction time of ethane hydrate was experimentally and theoretically studied in aqueous dispersion of silver nanoparticles (4.5, 9, 18, 27 and 36μM) at initial pressures of 1.5, 1.9 and 2.2MPa and temperatures of 276.15 and 277.65K. The results demonstrated that silver nanoparticles declined the hydrate induction time up to 97.5% compared to pure water. A new model for calculating induction time in the presence of nanoparticles was driven. The overall average absolute deviation between measured and predicted induction time was 14.34%. According to the results, the nucleation rate of ethane hydrate in the presence of silver nanoparticles was dramatically higher than pure water. The ethane hydrate/solution effective interfacial tension in the presence of nanoparticles and hydrate/nanoparticle wetting angle were estimated based on heterogeneous nucleation. The model illustrated that increase in nanoparticles concentration led to decrease in effective interfacial tension and wetting angle of ethane hydrate/nanoparticle.

Sonochemical synthesis and stabilization of concentrated antimicrobial silver‐chitosan nanoparticle dispersions

ABSTRACTThis work reports on a green synthetic route to produce concentrated aqueous dispersions of silver nanoparticles (AgNP) employing high‐intensity ultrasound (US) and chitosan (CS) as a nontoxic reducing agent for Ag+ salts and AgNP stabilizer. The sonication simultaneously boosted the synthesis and improved the stability of the AgNP, capping them with CS. Hybrid AgNP‐CS antimicrobial dispersions, stable for at least 6 months, were synthesized in a simple single step process. The use of US allowed for applying relatively mild processing temperatures (60 °C) and reaction time between 30 min and 3 h to obtain concentrated dispersions of AgNP that otherwise could not be obtained even after 72 h under mechanical stirring at the same reaction conditions. Upon sonication spherical AgNP‐CS with a size between 60 and 100 nm were generated, in contrast to the average diameter of ∼200 nm of the particles obtained by stirring. The antibacterial efficiency of the AgNP‐CS hybrids was evaluated against the medically relevant pathogens Staphylococcus aureus and Escherichia coli. The US‐synthesized AgNP‐CS showed more than three fold higher antibacterial activity compared to the particles obtained under stirring, due to their higher concentration and smaller size. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45136.

Rapid green synthesis of silver nanoparticles and nanorods using Piper nigrum extract

We report sun light driven rapid green synthesis of stable aqueous dispersions of silver nanoparticles and nanorods at room temperature using photoreduction of silver ions with Piper nigrum extract. Silver nanoparticles were formed within 3min of sun light irradiation following addition of Piper nigrum extract to the AgNO3 solution. The effects of AgNO3 concentration and irradiation time on the formation and plasmonic properties of biosynthesized silver nanoparticles were studied using UV–visible absorption spectroscopy. The morphology and structure of silver nanoparticles were well characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). The size of Ag nanoparticles increased with increase in irradiation time, leading to the formation of anisotropic nanostructures. Increasing the AgNO3 concentration resulted in the formation of Ag nanorods. UV–visible absorption studies revealed the presence of surface plasmon resonance (SPR) peaks which red shift and broaden with increasing AgNO3 concentration. We have demonstrated a facile, energy efficient and rapid green synthetic route to synthesize stable aqueous dispersions of silver nanoparticles and nanorods.

Effects of nanosilver-impregnation and alfalfa-intercropping on fluid transfer in downy black poplar wood

Effects of alfalfa-intercropping and nanosilver-impregnation were studied here on the specific gas permeability of 10-year old Populus nigra var. betulifolia. Specimens were impregnated with a 200 ppm aqueous dispersion of silver nanoparticles under 250 kPa pressure; the results were then compared with the un-impregnated specimens. The size range of silver nanoparticles was 10 to 80 nm. After the initial measurement, specimens were kept in vaporized chamber for six months (43±2°C, and 80±3% relative humidity); permeability was measured every month. Results showed that maximum specific longitudinal gas permeability was observed in the nanosilver-impregnated inner-wood specimens of the treatment with alfalfa (1614,4 × 10-13 m3 m-1), and minimum permeability was found in the un-impregnated outer-wood specimens of the treatment without alfalfa (491,7 × 10-13 m3 m-1) before the vaporization. Vaporized chamber made permeability decrease permeability at the first phases because of the absorption of water vapors and the consequent swelling; however, due to the proliferation of pits and perforation plates by fungi and molds, permeability was eventually increased. Antibacterial property of silver did not significantly decrease the growth of molds and fungi in the nanosilver-impregnated specimens.

Optimization of the synthesis and study of stable aqueous dispersions of silver nanoparticles used in medicine

Using chemical reduction, silver nanoparticle hydrosols were obtained and studied in a wide range of ratios of the initial reagents-NaBH4: AgNO3 from 0.1 to 10 and AOT: AgNO3 from 0 to 1—where AOT is dioctyl sulfosuccinate sodium salt. Silver hydrosols are studied using transmission electron microscopy, dynamic light scattering, UV spectroscopy, and ionometry. The optimal ratios of the initial reagents are determined, which make it possible to obtain samples with a narrow particle size distribution of 2 to 20 nm and average size of silver nanoparticles of 10 nm. The samples synthesized are stable over an extended period of time (up to six months) and contain an insignificant amount of ionic silver, which makes them useful for application in medicine.

Aqueous dispersions of silver nanoparticles in polyelectrolyte solutions

In this report, we present the versatile and effective technique, using environmental friendly reductant glucose, to prepare stable silver nanodispersions by reduction of Ag+ ions. Alternant copolymers of maleic anhydride with vinyl acetate and styrene sulphonate sodium acid salt polyelectrolytes were synthesized in aqueous solution and used as stabilizers. The formation of nano silver particles was confirmed by UV-Vis spectrophotometry and TEM measurements. Dynamic Light Scattering (DLS) measurements were needed to study how the reagents and their concentrations influence particle size. SEM images show the nanostructure of the hybrid films and indicate a strong interaction between the polyelectrolyte and the silver NPs. Moreover, the silver NPs could be stored for one year without observation of aggregates or sedimentation. The final solid products obtained after evaporating to dryness can be used to produce stable dispersions upon mixing with water. Few of the final products were found to exhibit a high antibacterial and antifungal activity. The possibility to obtain aqueous dispersions of silver nanoparticles in polyelectrolytes solutions was investigated. In order to synthesize stable silver nanodispersions, glucose, an environmental friendly reductant was used. The polyelectrolytes were alternant copolymers of maleic anhydride with vinyl acetate and styrene sulphonate sodium acid salt in aqueous solutions.

Effects of dry ice on gas permeability of nano-silver-impregnated Populus nigra and Fagus orientalis

Effects of dry-ice treatment (frozen CO(2) at -78.5°C) on gas permeability of untreated and nano-silver-impregnated poplar and beech specimens were studied here on the basis of their biological structure and woody mass as well as their vessel element types. A 200 ppm aqueous dispersion of silver nano-particles was used for impregnation; the size range of silver nano-particles was 20-80 nm. Dry-ice treatment increased gas permeability by 87 and 45% in poplar and beech, respectively. Nano-silver impregnation also increased gas permeability by 190 and 89% in poplar and beech, respectively. Dry-ice treatment on nano-silver-impregnated specimens increased gas permeability even more (31% increase in poplar but only 0.96% in beech). It may be concluded that dry-ice treatment on solid woods may be used as a practical method to increase permeability in species that because of their biological structures are impermeable; since this method alters the biological structure slightly and consequently decreases mechanical strength of solid woods insignificantly, it may substitute methods such as incising to increase permeability.

Green synthesis of colloidal silver nanoparticles using natural rubber latex extracted from Hevea brasiliensis

Colloidal silver nanoparticles were synthesized by an easy green method using thermal treatment of aqueous solutions of silver nitrate and natural rubber latex (NRL) extracted from Hevea brasiliensis. The UV–Vis spectra detected the characteristic surface plasmonic absorption band around 435 nm. Both NRL and AgNO 3 contents in the reaction medium have influence in the Ag nanoparticles formation. Lower AgNO 3 concentration led to decreased particle size. The silver nanoparticles presented diameters ranging from 2 nm to 100 nm and had spherical shape. The selected area electron diffraction (SAED) patterns indicated that the silver nanoparticles have face centered cubic (fcc) crystalline structure. FTIR spectra suggest that reduction of the silver ions are facilitated by their interaction with the amine groups from ammonia, which is used for conservation of the NRL, whereas the stability of the particles results from cis-isoprene binding onto the surface of nanoparticles. Therefore natural rubber latex extracted from H. brasiliensis can be employed in the preparation of stable aqueous dispersions of silver nanoparticles acting as a dispersing and/or capping agent. Moreover, this work provides a new method for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive.

Synthesis and spectroscopic studies of stable aqueous dispersion of silver nanoparticles

A facile approach for the synthesis of stable aqueous dispersion of silver nanoparticles (AgNPs) using glucose as the reducing agent in water/micelles system, in which cetyltrimethylammonium bromide (CTAB) was used as capping agent (stabilizer) is described. The evolution of plasmon band of AgNPs was monitored under different conditions such as (a) concentration of sodium hydroxide, (b) concentration of glucose, (c) concentration of silver nitrate (d) concentration of CTAB, and (e) reaction time. AgNPs were characterized by UV–visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy and FT-IR spectroscopy. The results revealed an easy and viable strategy for obtaining stable aqueous dispersion of AgNPs with well controlled shape and size below 30 nm in diameter.

Flexible transparent conductive coatings by combining self-assembly with sintering of silver nanoparticles performed at room temperature

Transparent conductive coatings are essential for fabrication of a variety of printed electronic devices such as flexible displays and solar cells. We report on a simple method to obtain such coatings by using aqueous dispersions of silver nanoparticles in an evaporative lithography process which is performed directly onto plastic substrates. In essence, a droplet containing silver nanoparticles is placed on top of a metallic mesh, instantaneously spreading over the mesh and the plastic substrate, and after the flow of the dispersion towards the wires of the mesh and drying, a transparent grid composed of the nanoparticles is formed. The silver nanoparticles are tailored to self-sinter upon short exposure to HCl vapors, due to the presence of polyacrylic acid salt on the surface of the particles. Therefore, immediate sintering of the silver nanoparticles in the thin lines of the grid occurs even at room temperature, enabling formation of transparent, flexible conductive grid on heat-sensitive substrates. The process yielded a conductive array having a very low sheet resistance, 9 ± 0.8 Ω/□, and a transparency above 75%. The application of the flexible conductive grid, which can replace conventional and expensive ITO, is demonstrated in an electroluminescent (EL) device.