Diameter Of Silver Nanoparticles Research Articles

One-Pot Biosynthesis of Carbon-Coated Silver Nanoparticles Using Palm Leaves as a Reductant and a Carbon Source.

In this study, carbon-coated silver nanoparticles (Ag@C NPs) were synthesized with a one-pot hydrothermal method using palm leaves as a reductant and a carbon source. SEM, TEM, XRD, Raman, and UV-vis analyses were employed to characterize the as-prepared Ag@C NPs. Results showed that the diameter of silver nanoparticles (Ag NPs) and the coating thickness could be controlled by changing the amount of biomass and the reaction temperature. The diameter ranged from 68.33 to 143.15 nm, while the coating thickness ranged from 1.74 to 4.70 nm. As the biomass amount and the reaction temperature increased, the diameter of Ag NPs and the coating thickness became larger. Thus, this work provided a green, simple, and feasible method for the preparation of metal nanocrystals.

ENHANCEMENT OF ANTIMICROBIAL MICRO CELLULOSE OF BAGASSE BY MODIFICATION WITH SILVER NANOPARTICLES

The preparation of microcellulose from sugarcane pulp enzymatically and its modification with silver nanoparticles had been conducted in this study. The objectives of this research were to prepare and characterize microfiber cellulose, and also its application as an antimicrobial material. Micro cellulose has been prepared by enzymatic methods and then continued with ultrasonication. The characterization of microfiber cellulose has been conducted by determining wavelengths with UV-Vis, functional groups with FTIR, surface image with SEM, and crystallinity with XRD. Synthesis of AgNPs had been conducted by bioreduction method using red betel leaf extracts via ultrasonication and stabilized by 0.05% starch solution. Characterization of silver nanoparticles had been conducted by determination of wavelength with UV-Vis and particle size with PSA. The antimicrobial tests of microcellulose have been determined by measuring of clear zones in Staphylococcus epidermidis, Pseudomonas aeruginosa, and Candida albicans. The characterization of microcellulose showed that wavelengths of micro cellulose at 300 nm, has C-O glycosidic bonds, the C=O, and lignin/hemicellulose. However, C=C lignin aromatic rings begin to disappear. Microcellulose size was 1 μm and crystallinity was 79.05%. The wavelengths in silver nanoparticles were shown at 424 nm. The diameter of silver nanoparticles was 88.6 nm. Micro cellulose with nanoparticle modification was the best in microbial inhibition

Modeling of plasmon resonance of silver nanoparticles on a silicon surface

Silver nanoparticles have unique optical properties due to resonance effects that arise due to the presence of conduction electrons in them. When these electrons interacte with photons, they can create localization of electric fields at the interfaces with the environment. Silver nanoparticles deposited on a transparent substrate are often used for research, while Ag nanostructures on Si are studied in this work. They have great potential for practical applications. The interaction of light with nanostructures can be described using various models (pseudo-dielectric functions, effective medium, thin-layer structures, etc.) and optical methods for the experimental determination of their parameters (refractometry, spectrophotometry). Bulk plasmon resonance is considered in this work, which is excited when plasmons are excited at their resonant frequency by an external electromagnetic wave. Calculations were performed for different diameters of silver nanoparticles on a silicon substrate with different structure periods. The calculated spectra are in good agreement with the experimental data of the obtained samples. As a result of the plasmon resonance modeling, the position of the plasmon resonance depends on the density of the arrangement of silver nanoparticles, with an increase in the displacement resonance towards the long-wavelength region.

Optical and Morphological Properties of Silver Nanoparticles Synthesis by Q-Switched Nd-YAG Laser

Abstract. Laser ablation of a silver target immersed in distilled water utilizing Nd: YAG laser with wavelengths of 532nm,1064nm, and 1320nm was carried out to fabricate silver nanoparticles. The synthesis of Ag NPs was carried out using various laser energy (200-1000 mJ) and different pulses (200-1000 pulse). Optical properties for the Ag nanoparticles solution were tested using UV-Visible spectrum, while the morphological properties for the Ag-nanoparticles solution after deposited on glass were tested using the atomic force microscope (AFM). The results showed that the synthesis of the Ag-nanoparticles using pulsed laser ablation in liquid (PLAL) (water) gives nanoparticles with homogeneous grain distribution and uniform surface roughness. It was found that the absorption peaks of Ag NPs increase by increasing the number of pulses shoot for the same laser wavelength and laser energy, and the reported maximum value of absorption peak is 0.363 when using 1000 pulses shoot. AFM results showed that the average diameter of the Ag NPs prepared by PLAL increases with increasing the laser wavelength. However, when using laser wavelengths of 1320nm,1064nm, and 532nm, the resulted average diameter of silver nanoparticles will be 55.38nm, 34.18nm, and 30.3nm, respectively. Finally, the average surface roughness of the Ag NPs prepared by PLAL increased with increasing the laser wavelength. The obtained average surface roughness of silver nanoparticles when using wavelengths of 1320nm,1064nm, and 532nm were 2.75nm, 1.19nm, and1.06nm, respectively.

Light harvesting enhancement using metal nanoparticles

Metal nanoparticles are very important for their optical properties when they interact with light. Metal nanoparticles have the ability to confine the collective oscillation of electrons, which is called localized surface plasmon resonance (LSPR). In this work, silver nanoparticles have been proposed to enhance light harvesting, which could be useful for different applications. Metal nanoparticles such as gold and silver nanoparticles have the ability to concentrate field in a very small space. In this study, gold and silver nanoparticles optical response was investigated using frequency domain simulation. The resonance wavelength of gold and silver nanoparticles was about 550 nm and 400 nm, respectively. Silver nanoparticles showed better LSPR performance than gold nanoparticles. Therefore, silver nanoparticles were chosen for optical field enhancement. Here silver nanoparticles were placed on a silicon substrate for optical field enhancement. To study the effect of size on the optical response of silver nanoparticles, the optical properties of this structure with different silver nanoparticles diameter values were investigated. Silver nanoparticles with 40 nm diameters showed a better optical response. To study the effect of the distance between silver nanoparticles on the optical response, different gap values were put between silver nanoparticles. The gap value of 4 nm showed a better optical response. The obtained results showed that the localized field is strongly dependent on the metal type, size, and space between nanoparticles. In addition, the optical field concentration can be controlled by tuning the size and space between silver nanoparticles. This will support localized field enhancement. The enhanced localized field will increase the field absorption near the surface, which can be beneficial for energy harvesting applications such as solar cells and detectors

Influence of nanostructure geometry on light trapping in solar cells

The aim of this research was to detect the influence of the silicon nanowires geometry and silver nanoparticles on the wafer surface on light trapping for application in solar cells with radial p–n junction. Si-NWs arrays were fabricated on p-type (100) silicon wafers with specific resistance of 10 Ω × cm. We used MacEtch method to form Si nanowires. In our study to deposit the additional silver nanoparticles on the surface of the nanowires, the flushing time was reduced to 10 min. The structural and optical properties of silicon nanowires were studied. The absorption, transmittance and reflectance spectra for periodic nanostructures with different parameters were calculated by FDTD (Finite-Difference Time-Domain) method. The FDTD method is a powerful numerical algorithm for direct solution of Maxwell’s equations. The realization of this method is discrete both in space and in time. The presented structures are described on a discrete mesh consisting of Yee cells and the Maxwell equations. They are solved discretely over time on this grid. As a result, through the method of the catalytic etching, we obtained nanowires of 0.5–2 μm in length and diameter in range of 50–100 nm. The diameter of silver nanoparticles was in the range of 20–50 nm. The reflection coefficient of light in wide spectral range was less than 1%. Reflection spectra peaked at the wavelength of 850 nm that points out on the influence of Ag nanoparticles.

Hydrodynamic Diameter of Silver Nanoparticles in Solutions of Nonionic Surfactants

Physicochemical characteristics of silver nanoparticles with known sizes are studied, depending on the concentration of nonionic surfactants and the concentration of the metal. Surfactants are used that form micelles of different sizes and different intensities of light scattering. It is shown that the surface tension and adhesion properties of solutions of nonionic surfactants are determined by the solvent in ranges of concentration lower than 1 mol/L. An approach based on spectrophotometry and viscosimetry is proposed that allows determination of the most likely reasons for discrepancies in the hydrodynamic diameter of nanoparticles in solutions of nonionic surfactants and the actual diameter of the nanoparticles.

Biofilm Eradication Using Biogenic Silver Nanoparticles.

Microorganisms offer an alternative green and scalable technology for the synthesis of value added products. Fungi secrete high quantities of bioactive substances, which play dual-functional roles as both reducing and stabilizing agents in the synthesis of colloidal metal nanoparticles such as silver nanoparticles, which display potent antimicrobial properties that can be harnessed for a number of industrial applications. The aim of this work was the production of silver nanoparticles using the extracellular cell free extracts of Phanerochaete chrysosporium, and to evaluate their activity as antimicrobial and antibiofilm agents. The 45–nm diameter silver nanoparticles synthesized using this methodology possessed a high negative surface charge close to −30 mV and showed colloidal stability from pH 3–9 and under conditions of high ionic strength ([NaCl] = 10–500 mM). A combination of environmental SEM, TEM, and confocal Raman microscopy was used to study the nanoparticle-E. coli interactions to gain a first insight into their antimicrobial mechanisms. Raman data demonstrate a significant decrease in the fatty acid content of E. coli cells, which suggests a loss of the cell membrane integrity after exposure to the PchNPs, which is also commensurate with ESEM and TEM images. Additionally, these biogenic PchNPs displayed biofilm disruption activity for the eradication of E. coli and C. albicans biofilms.

Non-spectral interferences in single-particle ICP-MS analysis: An underestimated phenomenon

This work demonstrates the effect of NaCl and carbon-related interferences on the analysis of arsenic and silver nanoparticles (NPs) by single-particle inductively coupled plasma mass spectrometry. Spectral interference caused by ArCl+ ions disturbing arsenic NPs analysis was eliminated using ammonia as reaction gas in a dynamic reaction cell of inductively coupled plasma mass spectrometer. In comparison to aqueous dispersions, non-spectral interferences caused by sodium lead to under-evaluation of arsenic and silver NPs diameter by about 7% and 15% at NaCl concentration of 450 mg L−1 and about 28% and 41% at NaCl concentration of 4500 mg L−1, respectively. As a consequence of lower transport efficiency, sodium non-spectral interferences also lead to about a 9% lower number of detected NPs for dispersions of both arsenic and silver NPs in 4500 mg L−1 NaCl. On the contrary, measurement of NPs in matrices containing methanol gives results where Ag and As NPs diameter is over-evaluated by about 3% and 15% at a methanol content of 1% (v/v) and about 6% and 20% at a methanol content of 2% (v/v), respectively, in comparison to aqueous dispersions. In addition, the organic carbon species behave as surfactants and increase the transport efficiency; this leads to an increase in the determined number concentration of NPs. In comparison to aqueous dispersions, this is over-evaluated by about 17% for Ag NPs and about 10% for As NPs at a methanol content of 5% (v/v).

Biosynthesis of Silver Nanoparticles from <i>Eucalyptus corymbia</i> Leaf Extract at Optimized Conditions

This study reports the biosynthesis of narrow range diameter silver nanoparticles at optimum conditions usingEucalyptus corymbiaas a reducing and stabilizing agent. Optimal conditions for biosynthesis of silver nanoparticles (AgNPs) were found to be; an extraction temperature of 90°C, pH of 5.7 a Silver Nitrate concentration of 1mM and AgNO3to plant extract ratio of 4:1. UV-Visible spectroscopy monitored the formation of colloidal AgNPs. The UV-Visible spectrum showed a peak around 425 nm corresponding to the Plasmon absorbance of the AgNPs. The size and shape characterization of the AgNPs was done using Transmission Electron Microscopy (TEM) techniques which revealed narrow range diameter (18-20 nm), almost monodispersed AgNPs, spherical in nature and with minimal agglomeration. Energy Dispersive X-ray (EDX) results showed the presence of two peaks at 3.0 and 3.15 keV in the silver region. The Fourier Transform Infrared-Spectra (FTIR) of the plant extract and the AgNPs gave rise to vibrational peaks at 3260 and 1634 wavenumbers which are due to the presence of OH and –C=C-functional groups respectively.

Thermal Stability of Surface Plasmon Resonance Absorption in а-С:Н〈Ag + TiО2〉 Nanocomposite Films

The thermal stability of surface plasmon resonance in a-C:H〈Ag〉 and a-C:H〈Ag + TiО2〉 nanocomposite films is studied. The films were deposited by ion-plasma magnetron sputtering of a combined graphite-metal target in the atmosphere of the argon and methane mixture. The structure and optical properties of nanocomposite films were studied using transmission electron microscopy and optical spectroscopy, respectively. It is found that surface plasmon resonance in the a-C:H〈Ag + TiО2〉 films persists to the annealing temperature of 450°C in argon atmosphere, whereas in a-C:H〈Ag〉 films, surface plasmon resonance disappears at the annealing temperature of 350°C. It is shown that annealing at 350°C leads to the significant increase in the diameter of silver nanoparticles in the structure of the a-C:H〈Ag〉 films. In the a-C:H〈Ag + TiO2〉 films, along with the appearance of silver nanoparticles with a large diameter, silver nanoparticles with a small diameter are present, which remain after annealing at this temperature. The higher thermal stability of surface plasmon resonance in the a-C:H〈Ag + TiО2〉 films is explained by the presence of TiO2 nanoparticles in the structure of films, which inhibit the coalescence of silver nanoparticles at high temperatures.

Silver nanocolloid as optical bistable device under continue wave laser illuminations

In this study, Kerr effect nonlinearity of silver nanocolloids due to thermal effect is investigated experimentally. Silver nanoparticles are synthesized by chemical reduction method in stable colloidal form in water. The diameter of silver nanoparticles is about 20 nm. Experimental results concerning the optical bistability of the nano-colloid are performed under CW laser illuminations. Two different CW laser beams (He-Ne and Nd-Yag lasers) were used to interact with a vertical Fabry-Perot interferometer containing a cell of nanocolloid. Hysteretic loops are observed due to optical bistability. Furthermore, nonlinear refractive indexes versus incident intensities are evaluated using close aperture z-scan method. It gives more precise values of nonlinear refractive indices that help in numerical drawing of Hysteretic loops. Experiments showed silver nanoparticles have good potential for semi-fast optical switcher devices in both red and green wavelengths.

Second-Harmonic Scattering from Metallic Nanoparticles in a Random Medium

We report the second-harmonic scattering intensity from silver nanoparticles dispersed in a linear random medium. The medium is formed by an aqueous solution of 80 nm diameter silver nanoparticles acting as nonlinear optical sources and 200 nm diameter latex nanospheres used as scattering centers. At photon scattering mean free paths longer than the ballistic photon path length, the second-harmonic intensity decreases exponentially due to the linear scattering of both the fundamental and harmonic beams. However, below a critical photon scattering mean free path, the decrease of the nonlinear optical intensity levels off. Polarization analysis further provides details about the transition from the ballistic to scattered second-harmonic photons. Because of the incoherent nature of the second-harmonic scattering process, we suggest that a lengthening of the interaction time of the fundamental photons with the nonlinear medium occurs.

Synthesis and evaluation of anti-inflammatory properties of silver nanoparticle suspensions in experimental colitis in mice.

The aim of our study was to investigate the effect of newly developed silver nanoparticle aqueous suspensions NanoAg1 and NanoAg2 in the mouse models mimicking ulcerative colitis and Crohn's disease. NanoAg1 and NanoAg2 were synthesized in aqueous medium with the involvement of tannic acid. To elucidate their anti-inflammatory activity, semi-chronic mouse models of inflammation induced by dextrane sulfate sodium addition to drinking water and intracolonic (i.c.) administration of 2,4,6-trinitrobenzenesulfonic acid were used. NanoAg1 and NanoAg2 (500mg/dm3, 100μl/animal, i.c., once daily) significantly ameliorated colitis in dextrane sulfate sodium- and 2,4,6-trinitrobenzenesulfonic acid-induced mouse models of colonic inflammation, as indicated by reduced macroscopic, ulcer and microscopic scores. The anti-inflammatory effect was dependent on the shape and diameter of silver nanoparticles, as indicated by weaker effect of NanoAg1 than NanoAg2. In addition, administration of NanoAg2, but not NanoAg1, modulated colonic microbiota, as indicated by reduced number of Escherichia coli and Clostridium perfringens, and increased number of Lactobacillus sp. Summarizing, NanoAg1 and NanoAg2 after administered i.c. effectively alleviate colitis in experimental models of ulcerative colitis and Crohn's disease in mice. Therefore, NanoAg1 and NanoAg2 administered i.c. have the potential to become valuable agents for the treatment of inflammatory bowel diseases.

Comparative study of silver nanoparticle permeation using Side-Bi-Side and Franz diffusion cells

Better understanding the mechanisms of nanoparticle permeation through membranes and packaging polymers has important implications for the evaluation of drug transdermal uptake, in food safety and the environmental implications of nanotechnology. In this study, permeation of 21 nm diameter silver nanoparticles (AgNPs) was tested using Side-Bi-Side and Franz static diffusion cells through hydrophilic 0.1 and 0.05 µm pore diameter 125 µm thick synthetic cellulose membranes, and 16 and 120 µm thick low-density polyethylene (LDPE) films. Experiments performed with LDPE films discarded permeation of AgNPs or Ag ions over the investigated time-frame in both diffusion systems. But controlled release of AgNPs has been quantified using semipermeable hydrophilic membranes. The permeation followed a quasi-linear time-dependent model during the experimental time-frame, which represents surface reaction-limited permeation. Diffusive flux, diffusion coefficients, and membrane permeability were determined as a function of pore size and diffusion model. Concentration gradient and pore size were key to understand mass transfer phenomena in the diffusion systems.

Scattering of light into thin film solar cells by rear located hemispherical silver nanoparticles

In this work, we numerically investigate the scattering and coupling efficiencies of the rear located hemispherical silver nanoparticles by using finite difference time domain simulations. The results indicate that the placement and diameters of silver nanoparticles have a strong impact on scattering efficiency. When the Ag particle extends into the silicon, the scattering from the particle is dominant and there is good coupling efficiency of the incident energy into the semiconductor. As the scattering cross-section increase with increasing diameter of the nanoparticle due to the surface plasmon polaritons resonance enhancement and the localized field intensity along the interface reach the maxima when a 60 nm rear located hemispherical particle extends to the silicon, the light trapping is more efficient. Such design could be used to improve light trapping for thin film solar cell devices.

Production of chiral matrices with hybrid silver–thiocholesterol nanosystems and study of their properties

A new type of chiral matrix based on silver–thiocholesterol hybrid nanosystems adsorbed on silica gel has been proposed. The molar ratio of stabilized thiocholesterol (L) ligand and silver (Ag) was found to have little effect on the size of the resulting silver nanoparticles (SNPs). The average diameter of SNPs was 2.7 ± 0.4, 2.2 ± 0.4, and 2.1 ± 0.6 nm upon the ratios Ag: L = 1: 5, Ag: L = 1: 2, and Ag: L = 1: 0.5, respectively. The resulting chiral matrices possess enantioselectivity relative to the 1,1’-binaphthyl-2,2’-diamine (BNDA) and trifluoroanthranyl ethanol (TFAE) optical isomers. The TFAE optical isomers were successfully separated using thin layer chromatography (α = 1.56).

Study of the formation of silver nanoparticles and silver nanoplates by chemical reduction method

The control of the diameter of silver nanoparticles, as well as the size and shape of silver nanoplates, is crucial for a lot of applications, from antibacterial solutions or surface treatment to biosensors. We synthesised silver nanoparticles and silver nanoplates from silver nitrate through a simple chemical reduction method in ambient conditions. Polyvinyl pyrrolidone (PVP) is used as both size controller and capping agent, while hydrogen peroxide and trisodium citrate (TSC) are used to control the nanoplates synthesis. Different solvents are used for obtaining the nanoparticles, i.e., water, ethylene glycol and ethanol. Standard characterisation was made by ultraviolet–visible spectrophotometry and transmission electron microscopy (TEM). The spherical nanoparticles solution presents a yellow colour, indicating the sole presence of Ag nanoparticles within a narrow diameter range as confirmed by the surface plasmon resonance peak which between 399 nm and 418 nm depends on the solvent. For the silver nanoplates, the colour of solutions varies from green, blue, violet, to purple when modifiers are added to the silver nanoparticle synthesis solution. We present the influence of the concentration of the different reagents on the size and shape of these nanostructures.

Evolution of silver nanoparticles in the rat lung investigated by X-ray absorption spectroscopy.

Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurements taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. We found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period.

Polydisperse Low Diameter ‘Non-Toxic’ Silver Nanoparticles Encapsulated by Rooibos Tea Templates

This work reports the synthesis of ‘non-toxic’ polydisperse, low diameter silver nanoparticles (AgNPs). Rooibos extracts at temperatures 25 °C, 30 °C, 50 °C, 70 °C and 90 °C were used. The effect of different extraction temperature on the % yield and nature of the AgNPs were investigated. The characteristics of the ‘green synthesis’ processed AgNPs were evaluated through UV-Vis spectroscopy, high resolution tunnelling microscopy (HRTEM), X-ray diffraction (XRD) and EDX techniques. Results indicated an increase in extraction temperature leads to more polyphenol extraction, increase in the AgNP % yield and greater absorbance. A yellow to brown to dark brown colour change observed during the synthesis indicated AgNPs formation. UV-Vis results indicated the AgNPs surface plasmon peaks at 440, 447, 450, 460 and 489 nm for the 25 °C, 30 °C, 50 °C, 70 °C, 90 °C respectively. SEM results revealed spherical nanosized particles with dense cores and lighter outer region with mean diameters for AgNPs ranged between 4.4-5.8 nm. EDX results indicated prominent Ag peaks at 3.10 keV. XRD results showed vaguely defined amorphous polyol peaks at below 2θ = 27°. The sharp peaks at 2θ = 38°, 45°, 66° and 77° which were assigned as 111, 200, 220 and 321 corresponded to the face-centred cubic crystalline silver phase.