Morphology Of Silver Nanoparticles Research Articles

Transport and Kinetic Effects on the Morphology of Silver Nanoparticles in a Millifluidic System

This work investigates the synthesis of silver nanoparticles of different shapes using silver nitrate as a precursor and ascorbic acid as a reducing agent in different reactors. The main focus of this work is to study the effect of capping agent concentrations and ratios of reducing agent to precursor concentrations (reactant ratios) on the shape and size of the nanoparticles synthesized. Three reactor configurations, namely, batch, straight millichannel, and spiral millichannel, are considered to study the transport effect on the morphology of silver nanoparticles synthesized. The kinetic effect on the particle morphology is studied by changing the capping agent concentrations and reactant ratios. It is shown that these variables play an important role in determining the nanoparticle shape and size. In this work, spherical nanoparticles (30–60 nm), triangular plates (80–200 nm), nanorods (130–150 nm), and bent wires (130–150 nm) morphologies are synthesized by controlling thermodynamic and kinetic parame...

Green synthesis of silver-nanoparticles from Annona reticulata leaves aqueous extract and its mosquito larvicidal and anti-microbial activity on human pathogens

Silver nanoparticles play a important role in controlling mosquito population as well as multi drug resistant pathogens without causing much harm to humans. In the present study was focused on green synthesis of silver nanoparticles against dengue causing vector (Aedes aegypti) and pathogens affecting humans. The synthesized silver nanoparticle was confirmed using UV- absorption spectrum range obtained at 416 nm, XRD, FTIR and HR-TEM analysis were used to determine the silver nanoparticle morphology and size with ∼6.48 ± 1.2–8.13 ± 0.18 nm and face centered cubic structure. The synthesized silver nanoparticles were exposed to fourth instar larvae of A. aegypti with different concentration (3–20 μg/mL) for 24 h and its elicit maximum mortality (100%) at their final concentration of 20 μg/mL and it’s LC50 value was 4.43 μg/mL and LC90 value was 13.96 μg/mL, respectively. The minimum inhibitory activities of the tested pathogens were 125, 31.25, 62.5, 62.6 and 62.5 μg/mL for the Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans respectively. Further, the synthesized silver nanoparticle shows a potent antimicrobial activity against all tested pathogens. Moreover the effect of silver nanoparticle against Red Blood Cells belonging to ‘O’ positive blood group were tested and does not cause higher hemolysis to the cells even at the highest concentration. Based on these finding, we strongly suggested that face centered cubic structured A. reticulata AgNPs is an eco-friendly and potent bio-medical agent and can be apply in wide range of application an alternative chemically synthesized metal nanoparticle.

Pyrene As a New Detector for Determining the Composition of Silver Nanoparticle Dispersions in Aqueous Solutions

It is proposed that the fluorescence of monomeric molecules of pyrene in solid matrices or in concentrated micellar solutions be used as a detector for determining the compositional homogeneity of silver nanoparticle (NP) dispersions in aqueous solutions synthesized in different ways. It is found that the morphology of silver NPs affects the change in the fluorescence intensity of monomeric molecules of pyrene in a certain (violet or blue) region of the pyrene optical spectrum. The observed phenomenon is attributed to the resonance of electronic transitions in the monomeric molecules of pyrene in regions with plasmon oscillations in silver nanoparticles. A new way of obtaining fluorescent silver NPs is found.

Effect of Concentration, pH and Time on the Morphology of Silver Nanoparticles Synthesized by Green Method using Phyllanthus Niruri and Solanum Nigrum Leaf Extracts

Effect of Concentration, pH and Time on the Morphology of Silver Nanoparticles Synthesized by Green Method using Phyllanthus Niruri and Solanum Nigrum Leaf Extracts

Poly-L-arginine Coated Silver Nanoprisms and Their Anti-Bacterial Properties.

The aim of this study was to test the effect of two different morphologies of silver nanoparticles, spheres, and prisms, on their antibacterial properties when coated with poly-L-arginine (poly-Arg) to enhance the interactions with cells. Silver nanoparticle solutions were characterized by UV–visible spectroscopy, transmission electron microscopy, dynamic light scattering, zeta potential, as well as antimicrobial tests. These ultimately showed that a prismatic morphology exhibited stronger antimicrobial effects against Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica. The minimum bactericidal concentration was found to be 0.65 μg/mL in the case of a prismatic AgNP-poly-Arg-PVP (silver nanoparticle-poly-L-arginine-polyvinylpyrrolidone) nanocomposite. The anticancer cell activity of the silver nanoparticles was also studied, where the maximum effect against a HeLa cell line was 80% mortality with a prismatic AgNP-poly-Arg-PVP nanocomposite at a concentration of 11 μg/mL. The antimicrobial activity of these silver nanocomposites demonstrates the potential of such coated silver nanoparticles in the area of nano-medicine.

Annealing Induced Morphology of Silver Nanoparticles on Pyramidal Silicon Surface and Their Application to Surface-Enhanced Raman Scattering.

This paper reports on a simple and cost-effective process of developing a stable surface-enhanced Raman scattering (SERS) substrate based on silver (Ag) nanoparticles deposited on silicon (Si) surface. Durability is an important issue for preparing SERS active substrate as silver nanostructures are prone to rapid surface oxidation when exposed to ambient conditions, which may result in the loss of the enhancement capabilities in a short period of time. Here, we employ the galvanic displacement method to produce Ag nanoparticles on Si(100) substrate prepatterned with arrays of micropyramids by chemical etching, and subsequently, separate pieces of such substrates were annealed in oxygen and nitrogen environments at 550 °C. Interestingly, while nitrogen-annealed Si substrates were featured by spherical-shaped Ag particles, the oxygen annealed Si substrates were dominated by the formation of triangular shape particles attached with the spherical one. Remarkably, the oxygen-annealed substrate thus produced shows very high SERS enhancement compared to the either unannealed or nitrogen annealed substrate. The hitherto unobserved coexistence of triangular morphology with the spherical one and the gap between the two (source of efficient hot-spots) are the origin of enhanced SERS activity for the oxygen-annealed Ag particle-covered Si substrate as probed by the combined finite-difference time domain (FDTD) simulation and cathodoluminesensce (CL) experiment. As the substrate has already been annealed in an oxygen environment, further probability of oxidation is reduced in the present synthesis protocol that paves the way for making a novel long-lived thermally stable SERS substrate.

Synthesis, characterization and studies on antioxidant activity of silver nanoparticles using Asphodelus aestivus Brot. aerial part extract

A rapid phytosynthesis of silver nanoparticles (AgNPs) using an extract from the aerial parts of Asphodelus aestivus Brot. was investigated in this study. Ultraviolet–visible spectroscopy, fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and zeta potential (ZP) were used to characterize the formation of silver nanoparticles (AgNPs). The antioxidant properties of these AgNPs were evaluated using DPPH, ABTS+ and hydrogen peroxide scavenging assays. The synthesized AgNPs were noticed through visual color change from yellow to gray brown. The UV–Vis spectrum exhibited an absorption band at around 440nm, which is a characteristic band for Ag. FT-IR measurement was carried out to identify the possible biomolecules responsible for capping and reducing agent for the Ag nanoparticles synthesized by A. aestivus aqueous extract. XRD results showed peaks at (200), (111), (110), (120), (330) and (210), which confirmed the presence of AgNPs with mono clinic crystals. The TEM image of silver nanoparticles shown that the morphology of silver nanoparticles was predominantly spherical. It could be concluded that A. aestivus extract can be used efficiently in the production of potential antioxidant AgNPs for commercial application.

Antimicrobial activity of silver nanoparticle colloids of different sizes and shapes against Streptococcus mutans

Silver nanoparticles stabilized with chitosan biopolymer are a new antibacterial agent for treatment of caries. To determine whether the size and morphology of silver nanoparticles in colloidal solution altered their antimicrobial activity, four colored colloids were characterized by ultraviolet–visible (UV–Vis) spectroscopy and transmission electron microscopy (TEM), and their antimicrobial activity [minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)] against reference stocks of Streptococcus mutans ATCC 25175 compared with chlorhexidine and silver diamine fluoride as controls. TEM revealed that the seed solution (SS) contained only spherical nanoparticles with size of 8.7 ± 3.1 nm whereas the other colloids had predominantly spherical nanoparticle shape, although colloid 1 (S1) contained 2.5% triangular nanoparticles. Colloid 2 (S2) had 15.9% triangular and 6.8% cylindrical nanoparticles, while 23.3% of the silver nanoparticles in colloid 3 (S3) were triangular and 1.5% were cylindrical. All the silver nanoparticle colloids showed antimicrobial activity with no statistically significant differences (p > 0.05) in MIC or MBC. The colloids showed antimicrobial activity higher than silver diamine fluoride (p 0.05). The size and shape of the nanoparticles did not affect the antimicrobial properties of the colored colloids. Thus, the antimicrobial activity of the colloids containing silver nanoparticles against Streptococcus mutans was considered equivalent to that of chlorhexidine, the gold-standard antibiotic in dentistry.

Shape-selective catalysis and surface enhanced Raman scattering studies using Ag nanocubes, nanospheres and aggregated anisotropic nanostructures.

Three morphologies of silver nanoparticles (Ag NPs) such as nanocubes, aggregated anisotropic Ag NPs, and nanospheres were prepared using polystyrene sulfonate (PSS) and citrate as stabilizing agents utilizing a simple wet-chemical and microwave heating route respectively. Ag nanocubes were prepared within one min through microwave heating whereas anisotropic Ag NPs and spherical Ag NPs via 5 and 30min of normal stirring at room temperature (RT) respectively. The shape effect of three different morphologies of Ag NPs were examined in catalysis reaction and in surface enhanced Raman scattering (SERS) studies. For catalysis experiments, reduction of various nitroaromatics was done taking excess NaBH4 in presence of those morphologically different Ag NPs as catalyst and the corresponding catalytic activity is ordered as: Ag nanospheres>aggregated anisotropic Ag NPs>Ag nanocubes. The highest catalytic rate of ∼1.34×10-1min-1 was observed with citrate capped Ag nanospheres. SERS study was done taking methylene blue (MB) as the Raman probe where a highest enhancement factor (EF) of ∼1.05×107 was observed with Ag nanospheres and the order of EF values is as follows: Ag nanospheres>Ag nanocubes>aggregated anisotropic Ag NPs. The highest catalytic and SERS activity of citrate stabilized spherical Ag NPs are attributed due to the fast electron transfer in catalysis and creation of more number of surface active 'hot spots' in SERS studies. In future, the overall process we highlighted here might found potential application for the preparation of other varieties of nanomaterials applicable to catalysis reaction and in SERS-based trace analysis of various biologically important molecules and fine chemicals.

Application of cone-cylinder combined fiber probe to surface enhanced Raman scattering

Owing to increasingly severe environmental pollution, food safety and other problems, higher and higher requirements for the detecting technique of poisonous and harmful biochemical molecules have been put forward. The conventional biochemical detector has the disadvantages of large size, high cost and inability to realize far-end and in-situ detection functions. Based on the requirements of the biochemical molecular detection technology for high sensitivity, miniaturization, far-end detection, insitu detection, real-time analysis and the like, a detection method using a fiber surface-enhanced Raman scattering (SERS) probe to carry out Raman signal detection has been put forward in recent years. The detection method not only realizes far-end and insitu detection functions, but also has a relatively high sensitivity. In this paper, a taper and cylinder combination type fiber probe is made by adopting a simple tube corrosion method, Under the situation of fixed temperature, cone-cylinder combined fiber probes with different diameters are obtained by controlling the corrosion time, and silver nanoparticles are bound to the surface of a silanized silicon dioxide fiber probe through electrostatic forces. Then, the sizes and morphologies of silver nanoparticles on the surface of the fiber probe are observed under a scanning electron microscope. Besides, the detection limit of a rhodamine 6G (R6G) solution is used to manifest both the activity and the sensitivity of the fiber probe, and the self-assembly time of the silver nanoparticles are further optimized to be 30 min and the diameter of the fiber probe to be 62 upm. When the concentration of a silver sol solution is constant, a high-sensitivity fiber SERS probe can be prepared. Through far-end detection, the detection limit of the R6G can reach 10-14 mol/L, and the enhancement factor is 1.36104. This work can serve as an experimental basis for a novel fiber surface-enhanced Raman scattering sensor in such aspects as high sensitivity and low cost. The studies of this paper are expected to provide an appropriate detection technique for rapid quantitative detection of biochemical molecules, and further provide a reference for various application fields of environmental monitoring and food safety analysis in future in terms of realizing rapid and accurate in-situ detection. Therefore, the fiber SERS probe has large application foreground in molecular detection.

Varying the morphology of silver nanoparticles results in differential toxicity against micro-organisms, HaCaT keratinocytes and affects skin deposition

The use of silver nanoparticles (Ag NPs) within the healthcare sector and consumer products is rapidly increasing. There are now a range of diverse-shaped Ag NPs that are commercially available and many of the products containing nanosilver are topically applied to human skin. Currently, there is limited data on the extent to which the antimicrobial efficacy and cytotoxicity of Ag NPs is related to their shape and how the shape of the Ag NPs affects their distribution in both intact and burn wounded human skin after topical application. In this study, we related the relative Ag NP cytotoxicity to potential skin pathogens and HaCaT keratinocytes in vitro with the shape of the Ag NPs. We employed multiphoton fluorescence lifetime imaging to map the distribution of the native and unlabeled Ag NPs after topical application to both intact and burn wounded human skin using the localized surface plasmon resonance signal of the Ag NPs. Truncated plate shaped Ag NPs led to the highest cytotoxicity against both bacteria (IC50 ranges from 31.25 to 125 μg/mL depending on the bacterial species) and HaCaT keratinocytes (IC50 78.65 μg/mL [95%CI 63.88, 96.83]) thus both with similar orders of magnitude. All Ag NPs were less cytotoxic than solutions of silver nitrate (IC50 of 7.85 μg/mL [95%CI 1.49, 14.69]). Plate-shaped Ag NPs displayed the highest substantivity within the superficial layers of the stratum corneum when topically applied to intact skin and the highest deposition into the wound bed when applied to burned ex vivo human skin relative to other Ag NP shapes.

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.

Preparation of graphene-Ag nanoparticles hybrids and their SERS activities

Surface-enhanced Raman scattering (SERS) substrates based on graphene and Ag nanoparticles hybrid structures with low cost, high uniformity were prepared by a standard process of immobilization of silver nanoparticles with 3-aminopropyltrimethoxysilane (APTMS). Thermal annealing was used for removing residual APTMS and adjusting the morphology of silver nanoparticles, and the effectiveness of this method was verified experimentally. The influence of annealing temperature, dipping duration, and APTMS volume on the distribution of Ag nanoparticles and Raman enhancement was investigated experimentally and analyzed in detail. Our samples were prepared under the preparation conditions of 10% ν/ν APTMS, dipping time of 48h, annealing temperature of 450°C, duration of 30min, and Ar flow rate of 40sccm. SERS activities with enhancement of 107 and relative standard deviation of <20% were observed using rhodamine 6G (R6G) as probe molecule with a concentration of 10−6M and 10−7M.

Influence of the Silica Support on the Structure and the Morphology of Silver Nanoparticles: A Molecular Simulation Study

We investigate the effect of the support on the structure and morphology of deposited metallic nanoparticles via molecular simulations at zero temperature. We focus on silver clusters in contact with a substrate which exhibits weak interactions, as amorphous silica, frequently used in atomic deposition experiments. Three levels of approximation are used to describe the substrate: (i) the smooth wall approximation where the support is modeled by a square-well whose depth is related to the adhesion energy of the nanoparticle, (ii) an atomistic model of flat amorphous silica obtained from Monte Carlo simulations with effective pair potentials, and (iii) the same silica substrate partially melted in order to roughen the surface at the nanometric scale. The metal–metal interactions are modeled using tight-binding semiempirical potentials, and the metal–silica interactions are modeled with Lennard-Jones potentials fitted to ab initio or experimental data. The icosahedron/decahedron/truncated octahedron sequence found for free Ag nanoparticles is shown to be affected by the substrate (square-well), which favors truncated octahedrons deposited on their (111) facets. The aspect ratio is shown to follow the Wulff–Kaishew theorem for large clusters. The introduction of an atomistic description of the flat SiO2 surface does not change the results significantly, while the presence of a nanometric roughness induces drastic changes. Vertex orientations of nanoparticles are possible in the surface hollows, and decahedron structures are slightly favored for sizes smaller than 1200 atoms.

Comparative study of cellulose/Ag nanocomposites using four cellulose types

The purpose of this study was to explore the influences of cellulose types on the cellulose/Ag nanocomposites via a microwave-assisted hydrothermal method. The cellulose/Ag nanocomposites were successfully fabricated using AgNO3 and four types of cellulose (cellulose nanocrystals (CNC), microcrystalline cellulose (MCC), cellulose fibers (CF), and holocellulose (HC)), in which the cellulose simultaneously served as the reducing agent and substrate for silver ions. The effects of different cellulose types on the products were investigated by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). The experimental results revealed that the cellulose types played a vital role on the size, number, and morphology of silver nanoparticles (AgNPs). It is believed that these results could be a guidance for the synthesis of cellulose/Ag nanocomposites in the future.

Green Biosynthesis of Silver Nanoparticles Using ‘Polygonum Hydropiper’ and Study its Catalytic Degradation of Methylene Blue

The green synthesis of silver nanoparticles with the small size and high stability paved the way to improve and protect the environment by decreasing the use of toxic chemicals and eliminating biological risks in biomedical applications. Plant mediated synthesis of silver nanoparticles is gaining more importance owing its simplicity, rapid rate of synthesis of nanoparticles and eco-friendliness. In this study, focus on biosynthesis of silver nanoparticles using Polygonum hydropiper extract and its catalytic degradation of hazardous dye, methylene blue has been highlighted. The rapid reduction of silver (Ag) ions was monitored using UV-Visible spectrophotometer and showed formation of silver nanoparticles within less than one hour with maximum absorption of silver nanoparticles at 430nm. The major functional groups present in the synthesis responsible for the formation of silver nanoparticles. It was identified by using Fourier Transform Infrared spectrophotometer (FTIR). Field Electron Scanning Microscope (FESEM) was used to characterise the nanoparticles synthesized using P.hydropiper. The morphology of silver nanoparticles was predominantly spherical and aggregated into irregular structure with average diameter of 60nm. In addition, this report emphasizes the effect of the silver nanoparticles on the degradation rate of hazardous dyes by sodium borohydride (NaBH4). The efficiency of silver nanoparticles as a promising candidate for the catalysis of organic dyes by NaBH4 through the electron transfer process is established in the present study.

Morphological change of silver nanoparticles by the effect of synthesis parameters

Metal nanoparticles are playing an essential role in this nano era. In the present study, silver nanoparticles(Ag NPs) were prepared by the green synthesis method from the extract of Ocimum tenuiflorum (tulasi) leaves. In the present study the morphology of silver nanoparticles was studied as a function of various synthesis conditions. Ag NPs were prepared using tulasi decoction and fresh tulasi juice. The flower like structure of Ag NPs was observed when tulasi decoction was used for the synthesis. Spherical Ag NPs formed when tulasi juice was used instead. The morphology and grain size of silver nanoparticles were obtained from SEM images. The elemental analysis of silver nanoparticles was done with EDS. The formation of Ag NPs was confirmed from the absorption spectrum. The absorption edge was observed in the range of 200-700nm.

An oxidation layer for regulating galvanically grown silver nanoparticles on silicon crystal for highly sensitive surface-enhanced Raman scattering measurements

In this study, a new method was developed in which an oxidation layer is used to regulate the morphology of silver nanoparticles (AgNPs) formed on Si crystals during galvanic displacement (GD). Using an oxidation layer yielded reproducible and stable AgNPs@Si substrates for sensitive surface-enhanced Raman scattering (SERS) measurements. The estimated SERS enhancement was at least an order of magnitude greater than for substrates prepared using a conventional GD method. The formation of Si–O− on the Si surface increased the adsorption of the AgNPs. Highly reproducible results were obtained, with a relative standard deviation of approximately 5%. To investigate the role of the oxidation layer and to optimize the reaction conditions, the oxidation layer thickness and chemical composition of the reaction solution were adjusted. The degree of aggregation in AgNP formation was mainly controlled by the thickness of the oxidation layer, whereas the size of the AgNPs was affected by both the concentration of AgNO3 and hydrofluoric acid in the reaction solution and the GD reaction time. When the optimized reaction conditions were used, the AgNPs@Si substrate had an enhancement factor of >107.

Морфология серебряных наночастиц, сформированных в поливинилспиртовой пленке

Морфология серебряных наночастиц, сформированных в поливинилспиртовой пленке

Silver nanoparticles with different size and shape: equal cytotoxicity, but different antibacterial effects

The influence of silver nanoparticle morphology on their dissolution kinetics in ultrapure water as well as their biological effect on eukaryotic and prokaryotic cells was examined.