Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Sintered silver nanoparticles(AgNPs)arewidely used in high-power electronics due to their exceptional properties.However,the material reliability is significantly affected by various microscopic defects.In this work,the three primary micro-defect types at potential stress concentrations in sintered AgNPs are identified,categorized,and quantified.Molecular dynamics(MD)simulations are employed to observe the failure evolution of different microscopic defects.The dominant mechanisms responsible for this evolution are dislocation nucleation and dislocation motion.At the same time,this paper clarifies the quantitative relationship between the tensile strain amount and the failure mechanism transitions of the three defect types by defining key strain points.The impact of defect types on the failure process is also discussed.Furthermore,traction-separation curves extracted from microscopic defect evolutions serve as a bridge to connect the macro-scale model.The validity of the crack propagation model is confirmed through tensile tests.Finally,we thoroughly analyze how micro-defect types influence macro-crack propagation and attempt to find supporting evidence from the MD model.Our findings provide a multi-perspective reference for the reliability analysis of sintered AgNPs.

Green Synthesis of Silver Nanoparticles Using Aqueous Orange and Lemon Peel Extract and Evaluation of Their Antimicrobial Properties

Green synthesis of silver nanoparticles (AgNPs) using aqueous extracts of orange and lemon peels, as a reducing agent, and silver nitrate salts as a source of silver ions is a promising field of research due to the versatility of biomedical applications of metal nanoparticles. In this paper, AgNPs were synthetized at different reaction parameters such as the type and concentration of the extracts, metal salt concentration, temperature, speed stirring, and pH. The antibacterial properties of the obtained silver nanoparticles against E. coli, as well as the physical and chemical characteristics of the synthesized silver nanoparticles, were investigated. UV-Vis spectroscopy was used to confirm the formation of AgNPs. In addition to green biogenic synthesis, chemical synthesis of silver nanoparticles was also carried out. The optimal temperature for extraction was 65˚C, while for the synthesis of AgNPs was 35˚C. The synthesis is carried out in an acidic environment (pH = 4.7 orange and pH = 3.8 lemon), neutral (pH = 7) and alkaline (pH = 10), then for different concentrations of silver nitrate solution (0.5 mM - 1 mM), optimal time duration of the reaction was 60 min and optimal stirring speed rotation was 250 rpm on the magnetic stirrer. The physical properties of the synthesized silver nanoparticles (conductivity, density and refractive index) were also studied, and the passage of laser light through the obtained solution and distilled water was compared. Positive inhibitory effect on the growth of new Escherichia coli colonies have shown AgNPs synthesized at a basic pH value and at a 0.1 mM AgNO3 using orange or lemon peel extract, while for a 0.5 mM AgNO3 using lemon peel extract.

Biosynthesis of Silver Nanoparticles with Clerodendron phlomoides Leave Extract:Particle Morphology,Antimicrobial Potential and Application

Silver nanoparticles are versatile nanomaterials that have found numerous applications in various fields.The use of plant extract for the synthesis of silver is a green and sustainable approach.Clerodendron phlomoides leaves extract has been found to contain various phytochemicals,such as phenols,flavonoids,tannins,and alkaloids,which possess reducing and stabilizing properties that can aid the production of silver particles.In this paper,morphological and topographical analyses were performed on silver nanoparticles.The biosynthesized silver nanoparticles showed antimicrobial potential against wound pathogens.SEM and TEM micrographs revealed that the particles were sphere and nanosized,which makes them suitable for various biomedical applications.

Hydrothermal synthesis of silver nanoparticles in Arabic gum aqueous solutions

Finely divided silver nanoparticles were synthesized via the hydrothermal method. Arabic gum （AG） was used as both the reductant and steric stabilizer without any other surfactant. By adjusting the reaction temperature, mass ratio of AG to AgNO3, and reaction time, silver nanoparticles with different morphological characteristics could be obtained. The products were characterized by UV-Vis, FTIR, TEM, SEM, and XRD measurements. It was found that temperature and AG played an important role in the synthesis of mono-disperse silver nanoparticles. Well dispersed and quasispherical silver nanoparticles were obtained under the optimal synthesis conditions of 10 mmol/L AgNO3, m（AG）/m（AgN03）= l：1, 160 ℃ and 3 h.

Synthesis of silver nanoparticles using leaves of Catharanthus roseus Linn.G.Don and their antiplasmodial activities

Objective:To develop a novel approach for the green synthesis of silver nanoparticles using aqueous leaves extracts of Catharanthus roseus(C.roseus) Linn.G.Don which has been proven aclive against malaria parasite Plasmodium falciparum(P.falciparum).Methods:Characterizations were determined by using ultraviolet-visible(UV-Vis) spectrophotometry,scanning electron microscopy(SEM).energy dispersive X-ray and X-ray diffraction.Results:SLM showed the formation of silver nanoparticles with an average size of 35-55 nm.X-ray diffraction analysts showed that the particles were crystalline in nature with face centred cubic structure of the hulk silver with the broad peaks at 32.4.46.4 and 28.0.Conclusions:It can be concluded that the leaves of C.roseus can he good source for synthesis of silver nanoparticle which shows aiitiplasmodial activity against P.falciparum.The important outcome of the study will he the development of value added products from medicinal plants C.roseus lor hionicdical and nanotechnology based industries.

Antibacterial Characterization of Silver Nanoparticles against E.Coli ATCC-15224

Silver nanoparticles of mean size 16 nm were synthesized by inert gas condensation （IGC） method. Crystalline structure, morphology and nanoparticles size estimation were conducted by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. Antibacterial activity of these silver nanoparticles as a function of particles concentration against gram-negative bacterium Escherichia coli （E. coli） was carried out in liquid as well as solid growth media. Scanning electron microscopy （SEM） and TEM studies showed that silver nanoparticles after interaction with E.coli have adhered to and penetrated into the bacterial cells. Antibacterial properties of silver nanoparticles are attributed to their total surface area, as a larger surface to volume ratio of nanoparticles provides more efficient means for enhanced antibacterial activity.

Rapid Preparation Process of Silver Nanoparticles by Bioreduction and Their Characterizations

Bioreduction as a novel nanoparticle synthesizing technology attracts increasing attention. Dried cells of the bacterium Aeromonas sp. SH10 rapidly reduced [Ag（NH3）2]^＋ to Ago in the solution into which some amount of OH^- was introduced. The surface plasmon resonance centered at 425 nm on the UV-vis spectra and five broad Bragg reflections on the XRD pattern showed that stable silver nanoparticles were formed during the bioreduction process. TEM and SEM observations suggested that the silver nanoparticles were uniform in size and well dispersed on the cells and in the solution. Therefore, silver nanoparticles could be prepared rapidly by this bioreduction technology.

Biogenesis of antibacterial silver nanoparticles using the endophytic bacterium Bacillus cereus isolated from Garcinia xanthochymus

Objective:To synthesize the ecofriendly nanoparticles,which is viewed as an alternative to the chemical method which initiated the use of microbes like bacteria and fungi in their synthesis.Methods:The current study uses the endophytic bacterium Bacillus cereus isolated from the Garcinia xanthochymus to synthesize the silver nanoparticles(AgNPs).The AgNPs were synthesized by reduction of silver nitrate solution by the endophytic bacterium after incubation for 3-5 d at room temperature.The synthesis was initially observed by colour change from pale white to brown which was confirmed by UV-Vis spectroscopy.The AgNPs were further characterized using FTIR,SEM-EDX and TEM analyses.Results:The synthesized nanoparticles were found to he spherical with the size in the range of 20-40 nm which showed a slight aggregation.The energy-dispersive spectra of the nanoparticle dispersion confirmed the presence of elemental silver.The AgNPs were found to have antibacterial activity against a few pathogenic bacteria like Escherichia coli,Pseudomonas aeruginosa,Staphylococcus aureus,Salmonella typhi and Klebsiella pneumoniae.Conclusions:The endophytic bacteria identified as Bacillus cereus was able to synthesize silver nanoparticles with potential antibacterial activity.

Catharanthus roseus:a natural source for the synthesis of silver nanoparticles

Objective:To develop a simple rapid procedure for bioreduction of silver nanoparticles(AgNPs)using aqueous leaves extracts of Catharanthus roseus(C.roseus).Methods:Characterization were determined by using UV-Vis spectrophotometry,scanning electron microscopy(SEM),energy dispersive X-ray and X-ray diffraction.Results:SEM showed the formation of silver nanoparticles with an average size of 67 nm to 48 nm.X-ray diffraction analysis showed that the particles were crystalline in nature with face centered cubic geometry.Conclusions:C.roseus demonstrates strong potential for synthesis of silver nanoparticles by rapid reduction of silver ions(Ag^+ to Ag^0).This study provides evidence for developing large scale commercial production of value-added products for biomedical/nanotechnology-based industries.

EFFECTS OF DIFFERENT FUNCTIONAL GROUP-CONTAINING ORGANICS ON MORPHOLOGY-CONTROLLED SYNTHESIS OF SILVER NANOPARTICLES AT ROOM TEMPERATURE

Silver nanoparticles with average particles sizes ranging from 2 to 131nm were manipulatively synthesized starting from silver nitrate using different functional group-containing organic modifiers at room temperature. The effects of the organic modifiers on the morphology of the resulting silver nanoparticles were strongly dependent on the intrinsic properties of the functional groups and the reducibility of the reductant. Numerous ether bonds （-0-）present in polyethylene glycol and Tween-80 were beneficial to the formation of silver nanoparticles with particle sizes of several nanometers in a narrow size distribution in both weak and strong reducing environments. Cetyltrimethylammonium bromide induced the formation of nanosized silver triangle plates in a weak reducing environment. The crystal growth of the silver nanoparticles with particle sizes of more than lOnm was postulated through an adhesion process of small-sized particles followed by a subsequent coalescence process under the present reaction conditions.

Effect of Silver Nanoparticles on Growth of Eukaryotic Green Algae

Silver nanoparticles,endowed with powerful antimicrobial property,are the most widely used nanomaterial in consumer products,with associated risk of their easy access to environment and freshwater ecosystems by surface runoff.Although toxic effects of nanosilver on bacterial,fungal and mammalian cells have been documented,its impact on algal growth remains unknown.Pithophora oedogonia and Chara vulgaris are predominant members of photosynthetic eukaryotic algae,which form major component of global aquatic ecosystem.Here we report for the first time that nanosilver has significant adverse effects on growth and morphology of these filamentous green algae in a dose-dependent manner.Exposure of algal thalli to increasing concentrations of silver nanoparticles resulted in progressive depletion in algal chlorophyll content,chromosome instability and mitotic disturbance,associated with morphological malformations in algal filaments.SEM micrographs revealed dramatic alterations in cell wall in nanoparticle-treated algae,characterized with cell wall rupture and degradation in Pithophora.Although these observations underscore severe deleterious effects of nanosilver on aquatic environment,the information can also be exploited as a bioengineering strategy to control unwanted and persistent growth of noxious algal weeds that clog the municipal water supply and water channels and produce fouling of water bodies.

Extracellular synthesis of silver nanoparticles using dried leaves of pongamia pinnata(L) pierre

Extract of oven dried leaves of Pongamia pinnata(L) Pierre was used for the synthesis of silver nanoparticles. Stable and crystalline silver nanoparticles were formed by the treatment of aqueous solution of AgNO_3(1m M) with dried leaf extract of Pongamia pinnata(L) Pierre. UV-visible spectroscopy studies were carried out to quantify the formation of silver nanoparticles. Transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy were used to characterize the silver nanoparticles. TEM image divulges that silver nanoparticles are quite polydispersed, the size ranging from 20 nm to 50 nm with an average of 38 nm. Water soluble heterocyclic compounds such as flavones were mainly responsible for the reduction and stabilization of the nanoparticles. Silver nanoparticles were effective against Escherichia coli(ATCC 8739), Staphylococcus aureus(ATCC 6538p), Pseudomonas aeruginosa(ATCC 9027) and Klebsiella pneumoniae(clinical isolate). The move towards extracellular synthesis using dried biomass appears to be cost effective, eco-friendly to the conventional methods of nanoparticles synthesis.

Green synthesis, antimicrobial and cytotoxic effects of silver nanoparticles mediated by Eucalyptus camaldulensis leaf extract

Objective: To investigate the environmental-friendly extracellular biosynthetic technique for the production of the silver nanoparticles(AgN Ps) by using leaf extract of Eucalyptus camaldulensis(E. camaldulensis). Methods: The NP were characterized by colour changes and the UV-visible spectroscopy. The cytotoxic effects of prepared AgN Ps was detected against four types of pathogenic bacteria, including two Gram-negative bacteria(Pseudomonas aeruginosa and Escherichia coli) and two Gram-positive bacteria(Staphylococcus aureus and Bacillus subtilis) by using agar well diffusion method. Results: A peak absorption value between 400-450 nm for the extract and the colour change to dark brown were corresponding to the plasmon absorbance of AgN Ps. On the other hand, aqueous extract of E. camaldulensis leaves could be effective against tested microorganisms which showed inhibition zones of 9.0-14.0 mm. Furthermore, biologically synthesized AgN Ps had higher ability to suppress the growth of the tested microorganisms(12.0-19.0 mm). Conclusions: Our findings indicated that extracellular synthesis of Ag NPs mediated by E. camaldulensis leaf extract had an efficient bactericidal activity against the bacterial species tested. The exact mechanism of the extracellular biosynthesis of metal NP was not well understood. Further studies are needed to highlight the biosynthesis process of AgN Ps and also to characterize the toxicity effect of these particles.

Green synthesis,antimicrobial and cytotoxic effects of silver nanoparticles using Eucalyptus chapmaniana leaves extract

Objective:To synthesize silver nanopaticles from leaves extract of Eucalyptus chapmaniana(E.chapmaniana)and test the antimicrobial of the nanoparticles against different pathogenic bacteria,yeast and its toxicity against human acute promyelocytic leukemia(HL-60)cell line.Methods:Ten milliliter of leaves extract was mixed with 90 mL of 0.01 mmol/mL or 0.02 mmol/mL aqueous AgNO_3 and exposed to sun light for 1 h.A change from yellowish to reddish brown color was observed.Characterization using UV-vis spectrophotometery and X-ray diffraction analysis were performed.Antimicrobial activity against six microorganisms was tested using well diffusion method and cytoxicity test using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide,a yellow tetrazole was obtained on the human leukemia cell line(HL-60).Results:UV-vis spectral analysis showed silver surface plasmon resonance band at 413 nm.X-ray diffraction showed that the particles were crystalline in nature with face centered cubic structure of the bulk silver with broad beaks at 38.50°and 44.76°.The synthesized silver nanoparticles efficiently inhibited various pathogenic organisms and reduced viability of the HL-60 cells in a dose-dependent manner.Conclusions:It has been demonstrated that the extract of E.chapmaniana leaves are capable of producing silver nanoparticles extracellularly and the Ag nanoparticles are quite stable in solution.Further studies are needed to fully characterize the toxicity and the mechanisms involved with the antimicrobial and anticancer activity of these particles.

Label-free colorimetric estimation of proteins using nanoparticles of silver

Metallic nanoparticles have received considerable attention in bioassays and diagnostics due to their unique surface plasmon resonance(SPR) properties.Gold nanoparticles have been employed for the development of SPR-based colorimetric bioassays.In the present report we have described a sensitive colorimetric approach for estimation of proteins,within a detection limit of 10?80 μg/m L,using unmodified silver nanoparticles.Besides the common advantages of colorimetric assay such as simplicity,high sensitivity,and low cost,our method has a label-free design and provides an important and attractive alternative to classical sensing probes and systems.The present work will contribute to the development of nanotechnology-based diagnostic tools.

Preparation, characterization, and antibacterial activity of γ-irradiated silver nanoparticles in aqueous gelatin

Colloidal silver nanoparticles （Ag-NPs） were obtained through γ-irradiation of aqueous solutions containing AgNO3 and gelatin as a silver source and stabilizer, respectively. The absorbed dose of γ-irradiation influences the particle diameter of the Ag-NPs, as evidenced from surface plasmon resonance （SPR） and transmission electron microscopy （TEM） images. When the γ-irradiation dose was increased （from 2 to 50 kGy）, the mean particle size was decreased continuously as a result of γ-induced Ag-NPs fragmentation. The antibacterial properties of the Ag-NPs were tested against Methicillinresistant Staphylococcus aureus （MRSA） （Gram-positive） and Pseudomonas aeruginosa （P.a） （Gram-negative） bacteria. This approach reveals that the γ-irradiation-mediated method is a promising simple route for synthesizing highly stable Ag-NPs in aqueous solutions with good antibacterial properties for different applications.

Antibacterial screening of silver nanoparticles synthesized by marine micro algae

Objective:To explore the biosynthesis of silver nanoparticles synthesized by marine microalgae. Methods:Marine microalgae was collected from Central Marine Fisheries Research Institute (CMFRI,tuticorin) and cultured in the lab.Silver nanoparticles synthesis were observed in normal and microwave irradiated microalgae and screened against human pathogens for the presence of antimicrobials.Results:The presence of silver nanoparticle was confirmed by UV-Visible spectroscopy at 420 nm by the presence of plasmon peak.Further confirmation was done by scanning electron microscope(SEM).Conclusions:These results not only provide a base for further research but are useful for drug development in the present and future.

Green synthesis of silver nanoparticles using aqueous extract of saffron(Crocus sativus L.) wastages and its antibacterial activity against six bacteria

Objective: To synthesis silver nanoparticles(Ag NPs) by using extract of saffron(Crocus sativus L.) wastages and to test their antibacterial activity against six bacteria.Methods: In this paper, the synthesis of Ag NPs using aqueous extract of saffron wastage as a green method without any chemical stabilizer and reducer is demonstrated. The synthesized Ag NPs were determined by UV–vis spectrum, high resolution transmission electron microscopy, X-ray diffraction, and Fourier transmission infrared spectroscopy analysis.Results: UV–vis spectrum showed a peak at 450 nm due to excitation of surface plasmon vibrations. Fourier transmission infrared spectroscopy showed that nanoparticles were capped with plant secondary metabolites. X-ray diffraction analysis also demonstrated that the size range of the synthesized nanoparticles was 12–20 nm. Transmission electron microscope image illustrated Ag NPs with spherical shape and an average size of15 nm. The result of antibacterial activities showed that the biosynthesized Ag NPs had an inhibiting activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Shigella flexneri and Bacillus subtilis.Conclusions: The biosynthesized Ag NPs showed significant antibacterial effect against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Shigella flexneri and Bacillus subtilis, so, it can be used in biomedical applications.

Luminescence intensification of lanthanide complexes by silver nanoparticles incorporated in sol-gel matrix

We present how the luminescence of europium RR-2-P-oxides complexes can be increased by interaction of electronic levels of the complex with the radiation field of silver nanoparticles （NPs）. The procedure by which silver NPs are formed in a sol-gel polyurethane matrix precursor was elaborated. The formed Ag NPs were combined with Eu complex incorporated in ormocer matrix. The emission spectra of the complexes without silver NPs were compared with spectra of the same complexes with addition of silver NPs. As the result of the interaction of the electronic levels of lanthaaide ligands with silver plasmons, dramatic increase of luminescence was observed.

Immobilized silver nanoparticles on silica gel as an efficient catalyst in nitroarene reduction

Nanoparticles have properties that can be fine-tuned by their size as well as shape.Hence,there is significant current interest in preparing nano-materials of small size dispersity and to arrange them in close-packed aggregates.This letter describes a way of synthesising silver nanoparticles and their protection to aggregate by silica gel.The combination of catalytic quantities of immobilized silver nanoparticles with reductive ability of NaBH_4 efficiently reduces aromatic nitroarenes to the corresponding amines in aqueous medium.Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogen and carboxylic acid groups.The silver particles immobilized on silica gel are stable in the presence of oxygen for several months.