DNA‐Mediated Morphological Control of Silver Nanoparticles

It is demonstrated that DNA can be used to control the synthesis of silver nanoplates with different morphologies using spherical silver seeds. UV–vis spectroscopy, transmission electron microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and Raman spectroscopy are used to characterize the synthesized nanoparticles. Silver nanoprisms are encoded by poly C and poly G, while silver flower bouquets and silver nanodiscs are synthesized using poly A and poly T, respectively. The length of DNA is found to have little effect on the morphology of silver nanoparticles. Moreover, the synthesized silver nanoplates are found to have high surface enhanced Raman scattering enhancement ability, good antibacterial activity, and good biocompatibility. These discoveries will broaden the application of DNA in nanoscience and will provide a new platform to investigate the interaction between DNA sequences and silver nanoparticles.     

Modeling of Silver Nanoparticle Synthesis in Ternary Reverse Microemulsion of Cyclohexane/Water/SDS

In the present study, a simple mathematical model has been developed for synthesis of silver nanoparticles. The silver nanoparticles have been synthesized in ternary reverse microemulsion of cyclohexane/water/sodium dodecyl sulfate (SDS). The silver nanoparticles were produced by reaction between silver nitrate in the water droplet core of one microemulsion and hydrazine as reducing agent in the water droplet core of another microemulsion. The dynamic behavior of process was modeled on mass balance equations which were solved using the finite difference method. The kinetic parameters of the critical number size (N _crit ), rate order of nucleation, and growth constants were estimated by minimizing the difference between the average particle size predicted by model and those obtained by experiments. The UV-Vis absorption spectra, transmission electron microscopy (TEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS) were used to analyze the structure and particle size distribution of silver nanoparticles.     

Biosynthesis of silver nanoparticles using Moringa oleifera leaf extract and its application to optical limiting

The Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving into an important branch of nanotechnology. The work presented here with the biosynthesis of silver nanoparticles using Moringa oleifera leaf extract as reducing and stabilizing agent and its application in nonlinear optics. The aqueous silver ions when exposed to Moringa oleifera leaf extract are reduced resulting in silver nanoparticles demonstrating the biosynthesis. The silver nanoparticles were characterized by UV-Visible, X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR) and transmission electron microscopy (TEM) techniques. TEM analysis shows a dispersion of the nanoparticles in a range of 5-80 nm with the average around 46 nm and are crystallized in face centred cubic symmetry. To show that these biosynthesized silver nanoparticles possess very good nonlinear properties similar to those nanoparticles synthesized by chemical route, we carried out the Z-scan studies with a 6 ns, 532 nm pulsed laser. We estimated the nonlinear absorption coefficient and compare it with the literature values of the nanoparticles synthesized through chemical route. The silver nanoparticles suspended in solution exhibited reverse saturable absorption with optical limiting threshold of 100 mJ/cm2.     

Synthesis of Silver Nanoparticles by a Laser–Liquid–Solid Interaction Technique

Silver nanoparticles of high chemical homogeneity have been synthesized by a novel laser–liquid–solid interaction technique from a solution composed of silver nitrate, distilled water, ethylene glycol, and diethylene glycol. Rotating nickel, niobium, stainless steel, and ceramic Al₂O₃ substrates were irradiated using a continuous-wave CO₂ laser and Q-switched Nd–YAG laser ( = 1064 and 532 nm). The silver nanoparticles were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe x-ray microanalysis (EPMA). The shape of silver particles was dependent on the chemical composition and laser parameters. The synthesis mechanism of silver nanoparticles has been proposed to occur primarily at the laser–liquid–substrate interface by a nucleation and growth mechanism.     

Biosynthesis of Ag nanoparticles and two‐dimensional element distribution in Arabidopsis

Metallic nanoparticles can be synthesised in living plants, which provide a friendly approach. In this work, the authors aimed to study the synthesis of silver nanoparticles (AgNPs) in Arabidopsis and the two‐dimensional (2D) distribution of Ag and other elements (Ca, P, S, Mg, and CI) in the Arabidopsis plant tissues. The concentrations of Ag in the plant tissues were determined by inductively coupled plasma‐atomic emission spectrometer, showing that the majority of Ag was retained in the roots. Transmission electron micrographs showed the morphology of AgNPs and the location in plant cells. The distributions of Cl and Ag were consistent in plant tissues by 2D proton‐induced X‐ray emission. In conclusion, this is the first report of the AgNP synthesis in Arabidopsis living plants and its 2D distribution of important elements, which provide a new clue for further research.Inspec keywords: silver, botany, atomic emission spectroscopy, antibacterial activity, nanoparticles, nanofabrication, transmission electron microscopy, chlorine, calcium, sulphur, phosphorusOther keywords: biosynthesis, two‐dimensional element distribution, metallic nanoparticles, silver nanoparticles, Arabidopsis plant tissues, inductively coupled plasma‐atomic emission spectrometry, transmission electron micrography, plant cells, 2D proton‐induced X‐ray emission, Arabidopsis living plants, Ag, Cl, Ca, P, S, Mg     

Enrichment of anodic MgO layers with Ag nanoparticles for biomedical applications

The growing fight against infections caused by bacteria poses new challenges for development of materials and medical devices with antimicrobial properties. Silver is a well known antimicrobial agent and has recently started to be used in nanoparticulate form, with the advantage of a high specific surface area and a continuous release of enough concentration of silver ions/radicals. The synthesis of MgO-Ag nanocomposite coatings by in situ deposition of silver nanoparticles during plasma electrolytic oxidation of a magnesium substrate is presented in this study. The process was performed in an electrolyte containing Ag nanoparticles under different oxidation conditions (i.e., current density, oxidizing time, silver nanoparticles concentration in the electrolyte). Surface morphology, phase composition and elemental composition (on the surface and across the thickness of MgO-Ag nanocomposite coatings) were assessed by scanning electron microscopy, X-ray diffraction, energy X-ray dispersive spectrometry and radio frequency glow discharge optical emission spectroscopy, respectively. The coatings were found to be porous, around 7 mum thick, consisting of a crystalline oxide matrix embedded with silver nanoparticles. The findings suggest that plasma electrolytic oxidation process has potential for the synthesis of MgO-Ag nanocomposite coatings.     

Synthesis of metastable silver-nickel alloys by a novel laser-liquid-solid interaction technique

Metastable silver-nickel alloys have been synthesized by chemical wetness and laser-liquid-solid interaction techniques from nitrate and acetate precursors of silver and nickel. Ethylene glycol and 2-ethoxyethanol were used as reductants in the synthesis reactions. Rotating niobium substrates immersed in the liquid precursor were irradiated by a continuos wave CO₂ and Nd-YAG laser ( = 1064 nm). The powders were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and high-resolution transmission electron microscopy (HRTEM). Two-phase alloys containing silver, nickel, and oxygen were fabricated, and the shape of the particles was found to be dependent on laser parameters and the chemical composition of the precursor solution. The synthesis mechanism of non-equilibrium Ag-Ni alloy nanoparticles has been proposed to occur primarily at the laser-liquid-solid interface by a nucleation and growth mechanism.     

Peanut skin extract mediated synthesis of gold nanoparticles,silver nanoparticles and gold–silver bionanocomposites for electrochemical Sudan IV sensing

Sustainable methods are needed for rapid and efficient detection of environmental and food pollutants. The Sudan group of dyes has been used extensively as adulterants in food and also are found to be polluting the soil and water bodies. There have been several methods for detection of Sudan dyes, but most of them are not practical enough for common use. In this study, the electrochemical detection efficiency and stability of gold nanoparticle (AuNPs), silver NPs and Au–Ag bionanocomposites, synthesised by peanut skin extract, modified glassy carbon electrode has been investigated. The synthesised nanomaterial samples were characterised, for their quality and quantity, using ultra–visible spectroscopy, inductive coupled plasma mass spectrophotometer, Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, high‐resolution transmission electron microscope and field emission scanning electron microscope. The nanomaterial hybrid electrodes showed great efficiency and stability in the detection of Sudan IV compared with the other previous electrodes. The peak current of the Sudan IV oxidation and reduction was found to be proportional to its concentration, in the range of 10–80 µM, with a detection limit of 4 µM. The hybrid electrodes showed 90% stability in detection for 20 cycles.Inspec keywords: gold, silver, nanoparticles, nanocomposites, biomedical materials, electrochemical sensors, dyes, nanofabrication, ultraviolet spectra, visible spectra, spectrophotometry, Fourier transform infrared spectra, X‐ray chemical analysis, transmission electron microscopy, scanning electron microscopy, field emission electron microscopyOther keywords: peanut skin extract mediated synthesis, gold nanoparticles, silver nanoparticles, gold–silver bionanocomposites, electrochemical Sudan IV sensing, electrochemical detection efficiency, modified glassy carbon electrode, ultra–visible spectroscopy, inductive coupled plasma mass spectrophotometer, Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, high‐resolution transmission electron microscope, field emission scanning electron microscope, oxidation, reduction, detection limit, Au, Ag, Au‐Ag     

Green synthesis of silver nanoparticles using Glaucium corniculatum (L.) Curtis extract and evaluation of its antibacterial activity

The metal nanoparticles, due to interesting features such as electrical, optical, chemical and magnetic properties, have been investigated repeatedly. Also, the mentioned nanoparticles have specific uses in terms of their antibacterial activity. The biosynthesis method is more appropriate than the chemical method for producing the nanoparticles because it does not need any special facilities; it is also economically affordable. In the current study, the silver nanoparticles (AgNPs) were obtained by using a very simple and low‐cost method via Glaucium corniculatum (L.) Curtis plant extract. The characteristics of the AgNPs were investigated using techniques including: X‐ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The SEM and TEM images showed that the nanoparticles had a spherical shape, and the mean diameter of them was 53.7 and 45 nm, respectively. The results of the disc diffusion test used for measuring the anti‐bacterial activity of the synthesised nanoparticles indicated that the formed nanoparticles possessed a suitable anti‐bacterial activity.Inspec keywords: silver, nanoparticles, antibacterial activity, nanomedicine, nanofabrication, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectraOther keywords: green synthesis, silver nanoparticles, Glaucium corniculatum Curtis extract, antibacterial activity, metal nanoparticles, biosynthesis method, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, SEM, TEM, spherical shape, disc diffusion test, Ag     

Biocompatible antimicrobial cotton fibres for healthcare industries: a biogenic approach for synthesis of bio‐organic‐coated silver nanoparticles

Cotton fibres coated with biogenically fabricated silver nanoparticles (SNPs) are most sought material because of their enhanced activity and biocompatibility. After successful synthesis of SNPs on cotton fibres using leaf extract of Vitex negundo Linn, the fibres were studied using diffuse reflectance spectroscopy, scanning electron microscopy, nanoparticle tracking analysis, energy dispersive X‐ray, and inductively coupled plasma atomic emission spectrometry. The characterisation revealed uniformly distributed spherical agglomerates of SNPs having individual particle size around 50 nm with the deposition load of 423 μg of silver per gram of cotton. Antimicrobial assay of cotton–SNPs fibres showed effective performance against pathogenic bacteria and fungi. The method is biogenic, environmentally benign, rapid, and cost‐effective, producing highly biocompatible antimicrobial coating required for the healthcare industry.Inspec keywords: cotton, health care, nanoparticles, coatings, silver, fibres, nanofabrication, scanning electron microscopy, X‐ray chemical analysis, atomic emission spectroscopy, plasma applications, microorganisms, biotechnologyOther keywords: biocompatible antimicrobial cotton fibre coating, healthcare industry, bioorganic‐coated silver nanoparticle synthesis, biogenically fabricated silver nanoparticle, SNP, leaf extraction, Vitex negundo Linn, diffuse reflectance spectroscopy, scanning electron microscopy, nanoparticle tracking analysis, energy dispersive X‐ray spectrometry, inductively coupled plasma atomic emission spectrometry, uniformly distributed spherical agglomerate, antimicrobial assay, pathogenic bacteria, fungi, Ag     

In vivo biosynthesis and spatial distribution of Ag nanoparticles in maize (Zea mays L.)

Nanoparticles (NPs), especially biosynthesised in living plants by absorbing soluble salts and reducing metal ions, are extensively used in various fields. This work aimed at investigating the in vivo biosynthesis of silver NPs (Ag‐NPs) in maize and the spatial distribution of the NPs and some important nutrient elements in the plant. The content of silver in plant was examined by inductively coupled plasma‐atomic emission spectrometer showing that Ag can be absorbed by plant as soluble salts. The NPs in different parts of maize plant were detected and analysed by transmission electron microscopy, demonstrating the synthesis of NPs and their transport from the root to the shoots. Two‐dimensional proton induced X‐ray emission of silver, chlorine and several nutrient elements elucidated the possible relationship between synthesis of NPs and several nutrient elements in plant tissues. To their knowledge, this is the first report of possibility of synthesis of Ag‐NPs in living plants maize (Zea mays L.). This study presents direct evidence for synthesis of NPs and distribution of related nutrient elements in maize, which has great significance for studying synthetic application of NPs in crop plants.Inspec keywords: atomic emission spectroscopy, nanoparticles, nanofabrication, crops, silver, transmission electron microscopy, X‐ray chemical analysis, sorption, chlorineOther keywords: maize plant, plant tissues, crop plants, spatial distribution, metal ion reduction, nutrient elements, inductively coupled plasma analysis, atomic emission spectrometry, Zea mays L., soluble salt absorbtion, transmission electron microscopy, proton induced X‐ray emission analysis, chlorine, silver nanoparticle biosynthesis process, Ag, Cl     

Humic acid assisted synthesis of silver nanoparticles and its application to herbicide detection

Silver nanoparticles have been synthesized by reduction of silver nitrate in the presence of humic acids (HA) which acted as capping agents. The HA protected nanoparticles were found to be sensitive to increasing concentrations of sulfurazon-ethyl herbicide in solution which induced a variation in color of the nanoparticles solution from yellow to purple. The effect of the humic acid concentration used in the nanoparticles synthesis was studied by varying the [Ag⁺:HA] ratio content from [1:1] to [1:100]. UV–Vis spectroscopy was used to monitor the extinction spectra of silver nanoparticles after the synthesis and in the herbicide sensing experiments. An average silver nanoparticles size of 5 nm was confirmed by transmission electron microscope (TEM). When exposed to increasing concentration of sulfurazon-ethyl (0, 100, 200, 300, 400, 500 ppm), the solution of nanoparticles was found to changes from yellow color to orange red and purple with increasing herbicide concentration.     

Comparing the growth of PVD silver nanoparticles on ultra thin fluorocarbon plasma polymer films and self-assembled fluoroalkyl silane monolayers

Adsorbed silver nanoparticles were prepared by means of electron beam evaporation of silver on ultra thin Si-supported heptadecafluoro-1-decene plasma polymer films and self-assembled heptadecafluorodecyl-trimethoxysilane monolayers. The morphology of the silver nanoparticles, characterized by their size, size distribution, shape and interparticle separation, was observed to depend on the type, chemical composition and surface energy of the sub-layer as well as the amount of silver deposited. Field emission-scanning electron microscopy was used to study the change in the morphology of the silver nanoparticles as a function of the preparation parameters. The silver nanoparticles on the ultra thin plasma polymer films demonstrated a much smaller and narrower size distribution due to the cross-linking within the film, which more effectively hinders the penetration of silver through the film in comparison to the self-assembled monolayers. Moreover, the optical properties of the resulting silver nanoparticles on the ultra thin fluorocarbon plasma polymers and their correlation to size and size distribution were investigated by spectroscopic ellipsometry in the wavelength range between 300 and 800?nm.     

Biosynthesis of silver nanoparticles by Pseudomonas spp. isolated from effluent of an electroplating industry

The aim of this study was to isolate and screen bacteria from soil and effluent of electroplating industries for the synthesis of silver nanoparticles and characterize the potential isolate. Soil and effluent of electroplating industries from Mumbai were screened for bacteria capable of synthesizing silver nanoparticles. From two soils and eight effluent samples 20 bacterial isolates were obtained, of these, one was found to synthesize silver nanoparticles. Synthesis of silver nanoparticle by bacteria was confirmed by undertaking characterization studies of nanoparticles that involved spectroscopy and electron microscopic techniques. The potential bacteria was found to be Gram‐negative short rods with its biochemical test indicating Pseudomonas spp. Molecular characterization of the isolate by 16S r DNA sequencing was carried out which confirmed its relation to Pseudomonas hibiscicola ATCC 19867. Stable nanoparticles synthesized were 50 nm in size and variable shapes as seen in SEM micrographs. The XRD and FTIR confirmed the crystalline structure of nanoparticles and presence of biomolecules mainly proteins as agents for reduction and capping of nanoparticles. The study demonstrates synthesis of nanoparticles by bacteria from effluent of electroplating industry. This can be used for large scale synthesis of nanoparticles by cost effective and environmentally benign mode of synthesis.Inspec keywords: biotechnology, effluents, soil, biochemistry, scanning electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, nanoparticles, electroplatingOther keywords: environmentally benign mode, large‐scale nanoparticles synthesis, proteins, biomolecules, Fourier transform infrared spectroscopy, X‐ray diffraction, SEM micrographs, pseudomonas hibiscicola ATCC 19867, 16S rDNA sequencing, molecular characterisation, biochemical test, gram‐negative short rods, potential bacteria, spectroscopy, electron microscopic techniques, soil, electroplating industries, effluent, pseudomonas spp, silver nanoparticles biosynthesis     

Silver nanoparticle production by Rhizopus stolonifer and its antibacterial activity against extended spectrum β-lactamase producing (ESBL) strains of Enterobacteriaceae

This report focuses on the synthesis of silver nanoparticles using the fungus, Rhizopus stolonifer and its antimicrobial activity. Research in nanotechnology highlights the possibility of green chemistry pathways to produce technologically important nanomaterials. Characterization of newly synthesized silver nanoparticles was made by UV-visible absorption spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy and atomic force microscope (AFM). TEM micrograph revealed the formation of spherical nanoparticles with size ranging between 3 and 20 nm. The biosynthesized silver nanoparticles (AgNPs) showed excellent antibacterial activity against ESBL-strains which includes E. coli, Proteus. sp. and Klebsiella sp.     

Bio-synthesis of gold and silver nanoparticles from Candida guilliermondii and their antimicrobial effect against pathogenic bacteria

In the present study we investigated the extra cellular synthesis of gold and silver nanoparticles by using the yeast Candida guilliermondii. The formation of noble metal nanoparticles was monitored by the UV-Visible spectroscopy. As prepared gold and silver nanoparticles showed distinct surface plasmon peaks at 530 nm and 425 nm respectively. Phase and morphology of the as synthesized materials were investigated by X-ray diffraction and electron microscopy techniques respectively. XRD patterns confirmed the formation of gold and silver nanoparticles with face centered cubic structures. Bio-TEM images showed the formation of near spherical, well dispersed gold and silver nanoparticles in the size range of 50-70 nm and 10-20 nm respectively. The biosynthesized nanoparticles were tested for their antimicrobial activity against five pathogenic bacterial strains. The highest efficiency for both gold and silver nanoparticles was observed against Staphylococcus aureus. A comparative study was also done to find the effect of chemically synthesized noble metal nanoparticles against the above test strains. Chemically synthesized particles had no antimicrobial activity against any of the pathogenic strains. The results obtained suggest that biosynthesized gold and silver nanoparticles can be used as effective antimicrobial agents against some of the potential harmful pathogenic microorganisms.     

Pulsed laser deposition of metal films and nanoparticles in vacuum using subnanosecond laser pulses

A study of silver, chromium, stainless-steel, and indium thin films prepared by subnanosecond laser deposition in vacuum is reported. We compare the laser ablation in vacuum at the weak- and tight-focusing conditions of a Ti:sapphire laser beam and analyze the nanoparticles synthesized in the latter case using absorption spectroscopy, x-ray fluorescence, atomic force microscopy, and scanning electron microscopy. Our results show that the nanoparticle formation can be accomplished using long laser pulses under tight-focusing conditions.     

In situ prepared polypyrrole–Ag nanocomposites: optical properties and morphology

Polypyrrole–silver (PPy–Ag) nanocomposites with various silver contents have been synthesized via a kinetically favorable one-step chemical oxidative polymerization process. The oxidant, ammonium persulfate, was used to oxidize pyrrole monomer for growing chains of PPy. And AgNO₃ was used as a precursor for metallic silver nanoparticles. The detailed characterization techniques, UV–Vis–NIR, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy (TEM), have been used to reveal electronic environment, structure, and morphology of composites as well as as-synthesized PPy. The synthesis environment prior to polymerization has also been investigated by absorption spectroscopy. The TEM images of PPy–Ag nanocomposites reveal that silver nanoparticles are deeply embedded into the polymer matrix in addition to surface adsorption. It is observed that the size distribution of inorganic nanoparticles (ca. 4–10 nm, depending on the metal ion concentrations) as well as structural morphology is altered by the initial concentrations of silver ions.     

Comparative Study of Antioxidant and Catalytic Activity of Silver and Gold Nanoparticles Synthesized From Costus pictus Leaf Extract

Biological synthesis of silver and gold nanoparticles using Costus pictus leaf extract(CPLE) and their potential in vitro antioxidant and catalytic activities were reported here. Formation of Costus pictus silver(CPAgN Ps) and gold(CPAuN Ps) nanoparticles was confirmed by UV-visible spectroscopy and their spherical shape by scanning electron microscopy. The synthesized nanoparticles gave strong signals for silver and gold in energy dispersive X-ray spectroscopy. The CPAgN Ps and CPAuN Ps had an average size of 46.7and 37.2 nm, respectively, as determined by dynamic light scattering particle size analyzer. Fourier transform infrared spectroscopy(FTIR) analysis indicated involvement of amine and carbonyl groups in the formation of CPAg NPs and CPAu NPs. Thermal stability of synthesized nanoparticles was assessed by thermogravimetric analysis-differential scanning calorimetry. CPAgN Ps, CPAuN Ps and CPLE exhibited tremendous antioxidant activity when being assessed by various in vitro assays, and their activity was comparable to standard antioxidants. CPAg NPs, CPAu NPs and CPLE also caused degradation of dyes like methylene blue and methyl red. While CPAgN Ps, CPAuN Ps and CPLE caused respective 85%, 42% and 30%degradation of methylene blue, they showed less activity against methyl red. These observations signify that such green methods open up new avenues in nanobiotechnology for the synthesis of nanoparticles with extensive industrial and biomedical applications.     

Biological synthesis of silver nanoparticles using the fungus Aspergillus flavus

The fungus, Aspergillus flavus when challenged with silver nitrate solution accumulated silver nanoparticles on the surface of its cell wall in 72 h. These nanoparticles dislodged by ultrasonication showed an absorption peak at 420 nm in UV-visible spectrum corresponding to the plasmon resonance of silver nanoparticles. The transmission electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodisperse silver nanoparticles (average particle size: 8.92 ± 1.61 nm) by the fungus. X-ray diffraction spectrum of the nanoparticles confirmed the formation of metallic silver. The Fourier transform infrared spectroscopy confirmed the presence of protein as the stabilizing agent surrounding the silver nanoparticles. These protein-stabilized silver nanoparticles produced a characteristic emission peak at 553 nm when excited at 420 nm in photoluminescence spectrum. The use of fungus for silver nanoparticles synthesis offers the benefits of eco-friendliness and amenability for large-scale production.