Shape Of Silver Nanostructures Research Articles

Impact of microwave synthesis time on the shape of silver nanostructures and their antibacterial activity

Silver is a well-known effective antibacterial and disinfectant material with relatively few side effects. Nanosilver derived from it, have strong antibacterial, antifungal and broad-spectrum antiviral properties. This study describes how the microwave synthesis durations of silver nanoparticles affect their shape, and the effect of the shapes of these nanoparticles on their antibacterial activity. The optical properties of the nanosilver were examined through UV-Vis absorption spectroscopy. The morphology of the grain was determined by transmission electron microscopy (TEM), and the crystallinity of the nanosilver was confirmed by X-ray diffraction (XRD). The antibacterial activities were assessed using bacterial pathogens Bacillus cereus and Bacillus megaterium, and were performed using the disk diffusion method. The obtained results show that (i) the shape and size of the nanosilver change when the microwave time is increased. They are of various sizes but almost all circular in shape when microwaved for 1.5 min, of larger sizes and different non-spherical geometric shapes after 3 min of microwave, and converted to nanowires after 5 min of microwave. (ii) Bacillus cereus and Bacillus megaterium were sensitive to all nanosilver but the antibacterial activity was more potent when the nanosilver possessed a defined shape than when they were silver nanowires.

Finite Element Analysis of Silver Nanorods, Spheres, Ellipsoids and Core-Shell Structures for Hyperthermia Treatment of Cancer.

The finite element analysis technique was used to investigate the suitability of silver nanorods, spheres, ellipsoids and core–shell structures for the hyperthermia treatment of cancer. The temperature of the silver nanostructures was raised from 42 to 46 °C, in order to kill the cancerous cells. The time taken by the nanostructures to attain this temperature, with external source heating, was also estimated. The heat transfer module in COMSOL Multiphysics was used for the finite element analysis of hyperthermia, based on silver nanostructures. The thermal response of different shapes of silver nanostructures was evaluated by placing them inside the spherical domain of the tumor tissue. The proposed geometries were heated at different time intervals. Optimization of the geometries was performed to achieve the best treatment temperature. It was observed that silver nanorods quickly attain the desired temperature, as compared to other shapes. The silver nanorods achieved the highest temperature of 44.3 °C among all the analyzed geometries. Moreover, the central volume, used to identify the thermal response, was the maximum for the silver nano-ellipsoids. Thermal equilibrium in the treatment region was attained after of heating, which made these structures suitable for hyperthermia treatment.

Green synthesis of silver nanostructures with amino acid-modified Pluronic F127 for antibacterial applications

The aim of this work was to evaluate the use of amino acid-functionalized Pluronic F127 derivatives in the synthesis of silver nanostructures (SNS), such as nanoparticles (SNP) and nanoclusters (SNC). Herein, glycine, L-alanine, and DL-alanine were used to functionalize poly(ethylene oxide) (PEO) end groups from the polymer chain via an esterification pathway. The esterified polymers were used for reducing and stabilizing SNS by a hydrothermal or a photo-assisted route (using a UVA light). The functionalized polymers were characterized by FTIR and the obtained SNS were characterized by UV–vis spectroscopy and TEM, which showed that the SNS obtained by the hydrothermal route are predominantly spherical, whereas those obtained by photo-assisted method give rise to rods and prisms. Kinetic studies showed that alanine and glycine form particles with different rates and that the different enantiomers (L and DL) influence the size and shape of SNS. The nanoparticles obtained by the two routes had their antibacterial efficiency tested against S. aureus by the Agar well diffusion method.

Shape selective silver nanostructures decorated amine-functionalized graphene: A promising antibacterial platform

Antibacterial nanoparticles offer great promise in various fields ranging from environmental to biomedical and biosensors. In this article we design a novel antibacterial material based on reduced graphene oxide (RGO) decorated with different shape of silver nanostructures. To control the size and shape of silver nanoparticles (AgNPs) on RGO sheets, composites of RGO decorated with different shape of AgNPs were synthesized using dimethylformamide (DMF) as reducing and coupling agent for reduction of graphene oxide (GO) and attachment of various shapes of AgNPs on RGO sheets. The results revealed that triangular AgNPs have highest antibacterial activity among different shapes of AgNPs against both gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) bacteria as representatives of bacteria species. In addition, results obtained in this study have showed that among different AgNPs/RGO nanocomposites, Ag triangles/RGO sample possess the best antibacterial property. It is suggested that the antibacterial activity of the prepared antibacterial platform, strongly depends on the shape of AgNPs on the surface of RGO, which could effectively use as antibacterial agent.

DEPENDENCE OF THE SURFACE-ENHANCED RAMAN SCATTERING SIGNAL ON THE SHAPE OF SILVER NANOSTRUCTURES GROWN IN THE SiO2 /n-Si POROUS TEMPLATE

Surface-enhanced Raman scattering is a powerful method used in chemoand biosensorics. The aim of this work was to determine the relationship between the signal of Surface-enhanced Raman scattering and the shape of silver nanostructures under the influence of laser radiation with different power.Plasmonic nanostructures were synthesized in silicon dioxide pores on monocrystalline silicon n-type substrate. The pores were formed using ion-track technology and selective chemical etching. Silver deposition was carried out by galvanic displacement method. Synthesis time was chosen as a parameter that allows controlling the shape of a silver deposit in the pores of silicon dioxide on the surface of single-crystal n-silicon during electrodeless deposition. Deposition time directly effects on the shape of metal nanostructures.Analysis of the dynamics of changing the morphology of the metal deposit showed that as the deposition time increases, the metal evolves from individual metallic crystallites within the pores at a short deposition time to dendritic-like nanostructures at a long time. The dependence of the intensity of Surface-enhanced Raman scattering spectra on the shape of the silver deposit is studied at the powers of a green laser (λ = 532 nm) from 2.5 μW to 150 μW on the model dye analyte Rodamin 6G. The optimum shape of the silver deposit and laser power is analyzed from this point of view design of active surfaces for Surface-enhanced Raman scattering with nondestructive control of small concentrations of substances.The silver nanostructures obtained in porous template SiO2 on n-type silicon substrate could be used as plasmon-active surfaces for nondestructive investigations of substances with low concentrations at low laser powers.

Green Synthesis of Different Shapes of Silver Nanostructures and Evaluation of Their Antibacterial and Cytotoxic Activity

Silver nanoparticles (NPs) have been demonstrated as a promising antibacterial candidate to fight against resistant pathogens. In this study, different shapes of silver nanostructures (i.e., sphere, rod, and cube) were synthesized by green methods. Morphology, size, and crystalline structure of the produced structures were characterized by UV–visible spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). For evaluation of antibacterial activity of silver nanostructures with various shapes, measurement of minimum inhibitory concentrations (MICs) was carried out against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria. The results showed that the concentration of silver nanostructures that prevents bacteria growth is different for each shape, the cubic and rod shape (with sharp edge and vertex) in lower concentrations being more effective than spherical nanoparticles. MTT assay to assess the toxicity of silver nanoparticles showed a concentration and shape-dependent decrease in cell viability in cancer human cells (MCF-7), signifying shape- and dose-dependent toxicity. In addition, the interaction of different nanostructures with serum albumin was evaluated. According to these results, AgNPs with sharper geometry resulted in protein degradation and higher toxicity as compared with smooth or spherical geometries. The results showed that the geometry of silver nanostructures can have quite a significant role in the definition of biological and antibacterial efficacy of NPs, which has significant implications in the design of NPs for various antibacterial applications and will require more consideration in the future.

Synthesis and Growth Mechanism of Silver Nanowires through Different Mediated Agents (CuCl2 and NaCl) Polyol Process

Silver nanowires (AgNWs) have been synthesized by polyol process through different mediated agents (CuCl2 and NaCl). The presence of cations and anions (Cu(II), Na+, and Cl−) has been shown to have a strong impact on the shape of silver nanostructures. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) show uniform nanowires. The UV‐vis spectra show that plasmon peak indicated the formation of nanowires. The X‐ray diffraction (XRD) pattern displayed that final product was highly crystallized and pure. The growth mechanism of AgNWs was proposed.

Controlling the Geometry of Silver Nanostructures for Biological Applications

Abstract Noble metals nanostructures, particularly silver, have attracted much attention in the fields of electronics, chemistry, physics, biology and medicine due to their unique properties which are strongly dependent on the size and shape of metal nanomaterials. This study discusses on silver nanostructures with different geometries including wire, cube, sphere and triangle prepared using solution-phase method and applied for antibacterial activities. X-ray diffraction (XRD), Ultra Violet Visible (UV-Vis) spectroscopy, Dynamic Light Scattering (DLS) and electron microscopy studies of different types of silver nanostructures revealed distinct optical and structural properties of an individual silver nanostructure. We have also evaluated the antibacterial activity of different shapes of silver nanostructures against Escherichia coli (E.coli), Bacillus and Staphylococcus. Results presents shape dependent antimicrobial activity of silver nanostructures.

Manipulation of silver nanostructures using supercritical fluids in the presence of polyvinylpyrrolidone and ethylene glycol

This study reports on a new method for manipulating the size and shape of silver nanostructures using supercritical carbon dioxide (CO 2) in the presence of polyvinyl pyrrolidone (PVP) and ethylene glycol (EG). The temperature and pressure of CO 2 as well as the ratio of the capping agent PVP to the precursor of silver nitrate are used to control the growth of the silver nuclei and grains during the synthesis of silver nanostructures in ethylene glycol. The as-synthesized nanostructures were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray powder diffraction (XRD). The results indicate that the aspect ratio of silver nanostructures, in particular, increases with an increase in the temperature and pressure of supercritical CO 2 from 3.5 to 50.

One-Pot Synthesis of Silver Nanoplates and Charge-Transfer Complex Nanofibers

We describe a facile one-pot process to synthesize Ag nanoplates by reducing silver nitrate with 3,3′,5,5′-tetramethylbenzidine (TMB) at room temperature. The silver nanoplates were highly oriented single crystals with (111) planes as the basal planes. TMB can be readily oxidized to charge-transfer (CT) complex between TMB, as a donor, and (TMB)2+, as an acceptor. The π−π interaction of the neutral amine (TMB) and diiminium structure (dication, TMB2+) result in the formation of one-dimensional CT complex nanofiber. The shape of silver nanostructures and the size of CT complex nanofibers could be controlled by tuning the initial molar ratio of TMB to Ag. This wet-chemical route provides a new concept for simultaneous preparing metal and CT complex nanostructures.

Preparation and Characterization of Different Shapes of Silver Nanostructures in Aqueous Solution

We have developed a new and simple one-pot synthetic approach for the preparation of single-crystalline rose-, spike-, and snowflake-shaped silver nanostructures (NSs) in aqueous solution. We obtained these variously shaped Ag NSs by carefully controlling the nature and concentration of the stabilizers, which included sodium acetate, sodium citrate, and poly(ethylene glycol). To the best of our knowledge, this paper is the first to describe the preparation of roseshaped Ag NSs, also called Ag nanoflowers (NFs), through such a simple synthetic route. The thus-prepared Ag NFs exhibited a specific surface area of 15.6 m g, a contact angle of 97.6 ± 2.2°, high conductivity (1.97 10 S/cm), and efficient optothermal conversion efficiency (the temperature rose 23.03 ± 0.21 °C after laser irradiation at 808 nm for 3 min). The snowflake-shaped Ag NSs allowed the enhancement of Raman scattering (SERS) signals of rhodamine 6G by a factor of 2.4 10, leading to a detection limit of 10 nM.

Preparation and Characterization of Different Shapes of Silver Nanostructures in Aqueous Solution

Preparation and Characterization of Different Shapes of Silver Nanostructures in Aqueous Solution