As-synthesized Silver Nanoparticles Research Articles

Synthesis of Monodispersed Lauric Acid Capped Silver Nanoparticles by Wet-Chemical Reduction Method

Silver nanoparticles with narrow distribution were prepared by a simple route in water in presence of lauric acid as the capping agents. The morphology and crystal structure of as-synthesized silver nanoparticles were analyzed by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The mass ratio of lauric acid and silver nitrate, the reaction temperature play important roles on the morphology and size of the silver nanoparticles. Well-dispersed silver nanopartilces with diameter of 8 nm were obtained when the mass ratio of lauric acid and silver nitrate was 1.2:1 and the reaction temperature was room temperature. It is also confirmed that the sol system was monodisperse nanosilver sol.

Electrolytic Deposition of Silver Nanoparticles Under “Principles of Green Chemistry”

In the present work, green synthesis of silver nanoparticles is investigated. The process is simple, environmentally friendly, cheaper and efficient. Instead of hazardous chemicals, “Tea extract” was used as a capping agent. In this process, electrolytic deposition of silver nanoparticles is done on a carbon rod wrapped with low-density polyethylene (LDPE). It was found that the current flowing in the circuit controls the size of the nanoparticles. A DC source was applied across the electrodes placed in a very dilute solution of AgNO3(0.01N), continuously magnetically stirred, over a period of 48 h at room temperature (30 °C). The as-synthesized silver nanoparticles were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. XRD patterns reveal that face-centered cubic structured silver particles were synthesized and the interplanar d-spacing of the corresponding lines presented in the powder XRD pattern match those of standard JCPDS file no. 04-0783. TEM analysis shows that silver nanoparticles of spherical and oval shape were synthesized. The particle size of the as-synthesized nanoparticles ranged from 5 to 100 nm for different values of current. The UV–vis spectroscopy shows the absorbance in visible range. As the particle size increases the absorption shifts towards higher wavelength region.

Studies on Interaction of Polysaccharide-Templated Silver Nanoparticles with Bovine Serum Albumin

In the present work, the interaction between bovine serum albumin (BSA) and as-synthesized silver nanoparticles (Oc-AgNPs) by using 4-acetamido-TEMPO-oxidized curdlan (Oc), as a reducing and stabilizing agent, was studied through fluorescence quenching method, ultraviolet visible spectrum (UV–Vis), and circular dichroism measurement. The results presented clearly indicate that the intrinsic fluorescence of BSA molecule was effectively quenched after the interaction with Oc-AgNPs by a static mechanism, which is further confirmed by UV–Vis analysis. The apparent binding constant (K), number of binding sites (n), and dissociation equilibrium constant (KD) were calculated to be 7.5 × 105 M−1, 1.03, and 3.0 ± 0.6 μM, respectively. Furthermore, a conformational change of BSA was also observed when the Oc-AgNPs–BSA interactant formed.

Multifunctionalization of cotton through in situ green synthesis of silver nanoparticles

A convenient method for in situ synthesis of silver nanoparticles was developed to realize the multifunction of cotton. The silver nanoparticles were obtained through reduction of silver ions by cotton under basic condition at room temperature. The as-synthesized silver nanoparticles achieved the coloration of cotton fibers. Heating increased the color strength of cotton fibers with silver nanoparticles. Mercerization treatment as a common finishing process enhanced the properties of cotton fibers modified by silver nanoparticles. The mercerized cotton exhibited brighter color and had very good colorfastness to washing. The cotton fibers treated with in situ synthesized silver nanoparticles possess strong antibacterial activity with excellent washing durability.

Fabrication, characterization and mosquito larvicidal bioassay of silver nanoparticles synthesized from aqueous fruit extract of putranjiva, Drypetes roxburghii (Wall.)

Highly stable nanoparticles of metallic silver with average dimension of 26.6nm were synthesized by a simple, cost-effective, reproducible and previously unexploited biogenic source viz. dried green fruits of Drypetes roxburghii (Wall.) (common name putranjiva). The as-synthesized silver nanoparticles (Ag NP) were characterized by their characteristic surface plasmon resonance absorption spectra, X-ray diffraction analysis, energy dispersive X-ray analysis and selected area electron diffraction study. The morphology of the particles was determined by high-resolution transmission electron microscopy. Fourier transform infrared analysis focuses some light on the chemical framework that stabilizes the nanoparticles. The analyses of the phytochemicals present in the fruit extract of the plant were also performed following standard protocol. Mosquito larvicidal bioassay with the Ag NPs was carried out with two mosquitoes, namely Anopheles stephensi Liston and Culex quinquefasciatus Say. The results show impressive mortality rate even at too low concentration of nanoparticle. Toxicity test on non-target organism shows no harmful effect during the study period.

Study on Bactericidal Effect of Biosynthesized Silver Nanoparticles in Combination with Gentamicin and Ampicillin on <i>Pseudomonas aeruginosa</i>

Silver nanoparticles are the most promising nanomaterial with antibacterial properties. Recent study of resistance to most potential antibiotics promotes research in the bactericidal activity of the silver nanoparticles. In this work, the effect of biosynthesized silver nanoparticles, in combination with gentamicin and ampicillin, on Pseudomonas Aeruginosa bacteria has been studied. Pseudomonas Aeruginosa is a common bacterium that can cause infections which are generalized as inflammation and sepsis. The results show that the bactericidal properties of the nanoparticles depends on the size of the as-synthesized silver nanoparticles as nanoparticles of diameter ~120 nm only have a direct interaction with the bacteria. It is observed that the antibacterial activities of antibiotics increase in the presence of AgNPs against test strains. Silver nanoparticles were synthesized elctrolytically using silver wire of 99% purity as anode and carbon rod wrapped with LDPE as cathode. 0.01 N Silver nitrate was used as an electrolyte. The process is termed as biosynthesis, because tea extract was used used as the capping agent which is also a very mild reducing agent. The polyphenols theaflavins and thearubigins, present in tea perform the role of stabilizing or capping agents due to their bulky and steric nature. A brown colored colloidal solution of silver nanoparticles is obtained. The as-synthesized silver nanoparticles were characterized using XRD, TEM and UV-Vis spectroscopy.

Green Synthesis of Silver Nanoparticles and their Antibacterial Activity

Silver nanoparticles have been prepared by the reduction of silver ions using respectively castor oil ( ricinus communis ), khat ( catha edulis ) and sun flower ( helianthus annuus ) leaf extracts as reducing and stabilizing agents. The as-synthesized material was characterized by using spectroscopic, XRD and TEM techniques. As-synthesized silver nanoparticles are found to have face centered cubic structure with average crystallite size 28 nm. and showed antimicrobial activity against Escherichia coli and Staphylococcus aureus .

Green synthesis of silver nanoparticles mediated by Pulicaria glutinosa extract.

The green synthesis of metallic nanoparticles (NPs) has attracted tremendous attention in recent years because these protocols are low cost and more environmentally friendly than standard methods of synthesis. In this article, we report a simple and eco-friendly method for the synthesis of silver NPs using an aqueous solution of Pulicaria glutinosa plant extract as a bioreductant. The as-prepared silver NPs were characterized using ultraviolet–visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. Moreover, the effects of the concentration of the reductant (plant extract) and precursor solution (silver nitrate), the temperature on the morphology, and the kinetics of reaction were investigated. The results indicate that the size of the silver NPs varied as the plant extract concentration increased. The as-synthesized silver NPs were phase pure and well crystalline with a face-centered cubic structure. Further, Fourier-transform infrared spectroscopy analysis confirmed that the plant extract not only acted as a bioreductant but also functionalized the NPs’ surfaces to act as a capping ligand to stabilize them in the solvent. The developed eco-friendly method for the synthesis of NPs could prove a better substitute for the physical and chemical methods currently used to prepare metallic NPs commonly used in cosmetics, foods, and medicines.

Bio-inspired fabrication of silver nanoparticles on nanostructured silica: characterization and application as a highly efficient hydrogenation catalyst

The design and facile green synthesis of supported metal-engineered nanoparticles with efficient catalytic activity has significant industrial importance. A biosynthetic and ecofriendly one-step reduction strategy has been developed through the protein-mediated in vitro biosynthesis of AgNPs on the surface of nanosilica. The as-synthesized silver nanoparticles supported on nanosilica (Ag@Nanosilica) were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDXA) elemental mapping, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The spectroscopic and electron microscopic studies demonstrated that the immobilized protein on the nanosilica surface served as a reducing, capping and stabilising agent, while sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed that the three proteins of 48, 38 and 36 kDa participated in the formation of Ag@Nanosilica material. The formation mechanism of AgNPs on nanosilica explained the origin of the biomineralization of metal nanoparticles in nature. The novel reusable Ag@Nanosilica exhibited enhanced catalytic activity for the hydrogenation of a model compound, namely, 4-nitrophenol. Overall our results will help to understand metal nanoparticle formation in the Earth’s crust and aid the design of “green” syntheses of novel nanoreactors.

Size-Controlled Green Synthesis of Silver Nanoparticles using Dual Functional Plant Leaf Extract at Room Temperature

ABSTRACT A simple synthesis of size-controlled silver nanoparticles using plant leaf extract at room temperature is described in this report. The reaction of AgNO3 with the leaf extract of Azadirachta indica in different concentrations and different reaction pH yields silver nanoparticles with control over size and distribution. The sizes of the as-synthesized silver nanoparticles were in the range between 10 to 63 nm and the size of nanoparticles were attributed to the concentration of leaf extract and pH of the reaction solution. The as-synthesized silver nanoparticles showed an excellent level of stability in water, and the nanoparticles formed in solution between pH 7 and pH 10.5 were not only stable in water, but also in NaCl solution and in different pH. The nanoparticles were characterized using various techniques.

Deoxycholate-Assisted Photochirogensis of Silver Nanoparticles

The Silver nanoparticles with chiroptical feature have been prepared via chiral transfer through supramolecular interaction during the photoirradiation of silver salt with the assistance of chiral environment provided by sodium deoxycholate at pH 9.7. The pH value plays a significant role for the formation of optically active silver nanoparticles, which may be due to the changes in distance and conformation caused by the addition of hydroxy anion. The as-synthesized silver nanoparticles exhibit the typical surface plasmon absorption, and most importantly, the positive circular dichroism signal in CD spectrum. This finding may be fundamentally important, on the one hand, in term of the fact that chiral photochemistry is extendable to the hot field of inorganic nanomaterials. On the other hand, the as-prepared chiral silver nanoparticles may find their application in chiral opto-electronic switches, the catalysts for asymmetric organic synthesis, or the host for chiral organic photochemistry.

Comparative Study on Bactericidal Effect of Silver Nanoparticles, Synthesized Using Green Technology, in Combination with Antibiotics on Salmonella Typhi

In this work bactericidal study of silver nanoparticles was taken up in combination with two standard antibiotics, ampicillin and gentamycin, for Salmonella Typhi. The antibacterial activities of antibiotics were increased in the presence of AgNPs against test strains. The higher enhancing effect was observed for ampicillin in comparison to gentamicin against test strains. Silver nanoparticles were synthesized elctrolytically using silver wire of 99% purity as anode and carbon rod wrapped with LDPE as cathode. Silver nitrate [of Merck] of 0.01N is used as an electrolyte. Here tea extract is added as capping and mild reducing agent. The polyphenols theaflavins and thearubigins, present in tea perform the role of stabilizing or capping agents due to their bulky and steric nature. A brown coloured colloidal solution of silver nanoparticles is obtained. The as-synthesized silver nanoparticles were characterized using XRD, TEM and UV-Vis spectroscopy.

Studies on fluorescence determination of nanomolar Cr(iii) in aqueous solutions using unmodified silver nanoparticles

In the current study we present a fluorescence probe for Cr(III) in aqueous solution employing as-synthesized silver nanoparticles (Ag NPs) without surface labeling by any extrinsic fluorophore. The principle of the method involves aggregation of Ag NPs by Cr(III) leading to a red-shift of the fluorescence emission peak from 420 to 684 nm for a corresponding excitation wavelength of 340 nm. The UV-visible absorption spectral studies, dynamic light scattering measurements, and scanning electron microscopy (SEM) corroborated the aggregation of the Ag NPs upon interaction with Cr(III). Under the optimized conditions, a good linear relationship (correlation coefficient r = 0.975) was observed between concentration of Cr(III) and the fluorescence intensity at 684 nm in the range of 1 × 10−3 to 2 × 10−9 M (50 mg L−1 to 100 ng L−1). The reported probe has a limit of detection as low as 2 nM, which, to the best of our knowledge, is the lowest ever reported for the fluorescence detection of Cr(III). The developed sensor was successfully tested with chromium containing real samples, such as groundwater and fresh water, demonstrating potential application in the field of environmental sensing.

Study of mechanism of enhanced antibacterial activity by green synthesis of silvernanoparticles

The extensive use of silver nanoparticles needs a synthesis process that is greener withoutcompromising their properties. The present study describes a novel green synthesisof silver nanoparticles using Guava (Psidium guajava) leaf extract. In order tocompare with the conventionally synthesized ones, we also prepared Ag-NPs bychemical reduction. Their optical and morphological characteristics were thoroughlyinvestigated and tested for their antibacterial properties on Escherichia coli. The greensynthesized silver nanoparticles showed better antibacterial properties than theirchemical counterparts even though there was not much difference between theirmorphologies. Fourier transform infrared (FTIR) spectroscopic analysis of the usedextract and as-synthesized silver nanoparticles suggests the possible reduction ofAg + by the water-soluble ingredients of the guava leaf like tannins, eugenoland flavonoids. The possible reaction mechanism for the reduction ofAg + has been proposed and discussed. The time-dependent electron micrographs and thesimulation studies indicated that a physical interaction between the silver nanoparticlesand the bacterial cell membrane may be responsible for this effect. Based on the findings, itseems very reasonable to believe that this greener way of synthesizing silver nanoparticles isnot just an environmentally viable technique but it also opens up scope to improve theirantibacterial properties.

Influence of synthesis temperature on synthesis of PVA-stabilised silver nanoparticles

Polyvinyl alcohol (PVA)-stabilised silver nanoparticles have been synthesised by the simple reduction process at different temperatures ranging from 60 to 90°C. The as-synthesised silver nanoparticles were analysed by X-ray diffraction (XRD), energy-dispersive analysis of X-rays, transmission electron microscope, UV–vis absorption spectroscopy and Fourier transform infrared (FTIR) spectroscopy. XRD studies showed that the samples exhibited cubic structure. The average particle size was found to be ∼50 nm. FTIR spectra revealed that the synthesised nanoparticles were successively capped by PVA. Optical absorption spectra confirmed the uniformity of as-prepared silver nanoparticles and the absorption peak was observed in the range 390–421 nm.

Highly bacterial resistant silver nanoparticles: synthesis and antibacterial activities

In this article, we describe a simple one-pot rapid synthesis route to produce uniform silver nanoparticles by thermal reduction of AgNO3 using oleylamine as reducing and capping agent. To enhance the dispersal ability of as-synthesized hydrophobic silver nanoparticles in water, while maintaining their unique properties, a facile phase transfer mechanism has been developed using biocompatible block co-polymer pluronic F-127. Formation of silver nanoparticles is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. Hydrodynamic size and its distribution are obtained from dynamic light scattering (DLS). Hydrodynamic size and size distribution of as-synthesized and phase transferred silver nanoparticles are 8.2 ± 1.5 nm (σ = 18.3%) and 31.1 ± 4.5 nm (σ = 14.5%), respectively. Antimicrobial activities of hydrophilic silver nanoparticles is tested against two Gram positive (Bacillus megaterium and Staphylococcus aureus), and three Gram negative (Escherichiacoli, Proteusvulgaris and Shigellasonnei) bacteria. Minimum inhibitory concentration (MIC) values obtained in the present study for the tested microorganisms are found much better than those reported for commercially available antibacterial agents.

English

Stable aqueous monodispersed silver nanoparticles were synthesised by reducing silver nitrate using various sugars such as glucose, fructose, lactose, and sucrose at 55-60 oC. A mixture of two stabilising agents, polyvinyl pyrrolidone (PVP) of molecular weight (MW 40, 000) and gelatin plays a decisive part in controlling size and shape of superfine silver nanoparticles. Using PVP, better control of particle size was obtained, whereas a mixture of PVP, and gelatin resulted in sea urchin kind of structure. Effects of several processing parameters such as pH, quantities of alkaline solution, reaction time, concentration of stabilising agent, and the metal/dispersant ratio were investigated. The suspensions were stable for at least one week. Silver nanoparticles can be easily collected by centrifugation on mixing with sufficient amount of acetone. Structural characterisation of synthesised silver nanoparticles was carried out by X-ray diffraction (XRD), which shows that the as-synthesised silver nanoparticles are face-centered cubic crystalline. Chemical characterisations of as-synthesized silver nanoparticles were done using inductively-coupled plasma-optical emission spectrometry (ICP-OES) and LECO gas analysers. The optical properties of silver nanoparticles were monitored using UV-Vis spectrophotometer. Role of stabilising agent in protecting the silver nanoparticles was studied using fourier transform infrared spectroscopy (FTIR). Particle size and distribution were characterised using smallangle X-ray scattering (SAXS), zeta particle size analyser (PSA), scanning electron microscopy, and transmission electron microscopy. The average particle size of the as-synthesised silver nanoparticles was 35 nm.Defence Science Journal, 2009, 59(4), pp.447-455, DOI:http://dx.doi.org/10.14429/dsj.59.1545

Monodisperse Silver Nanoparticles Synthesized by a Microwave-Assisted Method

Silver nanoparticles with an average size of about 20 nm are synthesized in a colloidal solution with the aid of microwave irradiation. Neither additional reductant nor stabilizer is required in this microwave-assisted method. The color of the colloidal solution is found to be dark green, different from the characteristic yellow of silver colloidal solutions. The silver nanoparticles in the colloidal solution have a narrow size distribution and large yield quantity. UV-visible absorption spectroscopy analysis reveals that the as-synthesized monodisperse silver nanoparticles have exceptional optical properties. Raman spectroscopy measurements demonstrate that these silver nanoparticles exhibit a notable surface-enhanced Raman scattering ability.

Supercritical carbon dioxide-assisted synthesis of silver nano-particles in polyol process

Silver nano-particles have been synthesized by the polyol process with the assistance of supercritical carbon dioxide (SCCO 2), with silver nitrate used as the base material, polyvinyl pyrrolidone (PVP) as the stabilizer for the silver clusters, and ethylene glycol as the reducing agent and solvent. Polyvinyl pyrrolidone not only protected nano-size silver particles from aggregation, but it also promoted nucleation. The silver nano-particles synthesized by SCCO 2 were smaller and had a more uniform dispersion than those made under the same conditions by the conventional heating process. The superior fluidity and diffusivity of SCCO 2 reduced the viscosity of the ethylene glycol and penetrated the entire solution to help increase the contact frequency of silver ions and electrons and in doing so, nucleation from silver ion to seed crystal was increased. The as-synthesized silver nano-particles were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM) and UV–vis spectrophotometer. The UV–vis spectrum of the silver nano-particles was sensitive to particle size. In particular, high dispersion stability synthesized silver nano-particles could be obtained by binding PVP on their surface in this work.

Gamma-radiation synthesis, characterization and nonlinear optical properties of highly stable colloidal silver nanoparticles in suspensions

Colloidal silver nanoparticles were synthesized by gamma-radiation method and stabilized by poly(4-vinylpyridine) to form highly stable suspensions in ethylene glycol. X-ray diffraction, transmission electron microscopy, and optical techniques were used to characterize the colloidal nanoparticles and study their formation process. Optical nonlinearity, induced by 8 ns laser pulses from a frequency-doubled Nd:YAG laser at 532 nm , was investigated by using Z-scan technique, indicating that the as-synthesized colloidal silver nanoparticles had obvious negative refractive nonlinearity.