Shape Of Silver Nanoparticles Research Articles

Phytofabrication of silver nanoparticles from Illicium verum fruit extract and its role in Cr+6 removal: a comparative analysis

ABSTRACT Herein, using Illicium verum (IV) aqueous fruit extract, spherical shape silver nanoparticles (IV-AgNPs) of 40 nm average size with typical SPR at 422 nm were synthesised through the one-pot chemical reduction method. In the presence of Cr+6, IV-AgNPs rapidly changed from yellow to pink colour, with immediate SPR quench at 422 nm and new peak appearance at 510 nm, suggesting carboxylate groups involvement in AgNPs synthesis and Cr+6 interaction, respectively. Clusters were formed in Cr+6 presence; as a result, IV-AgNPs’ zeta potentials changed from −24.1 to 14 mV. Moreover, with the lowest limit of detection (22.1 nM), IV-AgNPs displayed higher potential for Cr+6 adsorption in aqueous medium. The Langmuir isotherm predicts monolayer adsorption on a homogeneous surface of both adsorbents via chemisorption kinetics with adsorption capacity of 1511.65 and 720.35 mg/g for IV-AgNPs and IV fruit extract, respectively. Calculated thermodynamic values of -∆G°, +∆H°, and +∆S° indicate spontaneity, randomness, and endothermicity of the adsorbate system(s). Akaike information criterion ranking alignment and kinetics equilibrium for adsorbents showed that the Elovich plot and intra-particle diffusion produced the best output in comparison to other models. These findings indicate adsorption dynamics are controllable for both adsorbents, but the size-dependent properties of IV-AgNPs significantly improve interaction efficiency for Cr+6 adsorption.

Impacts of Differentially Shaped Silver Nanoparticles with Increasingly Complex Hydrophobic Thiol Surface Coatings in Small-Scale Laboratory Microcosms.

We investigated the impacts of spherical and triangular-plate-shaped lipid-coated silver nanoparticles (AgNPs) designed to prevent surface oxidation and silver ion (Ag+) dissolution in a small-scale microcosm to examine the role of shape and surface functionalization on biological interactions. Exposures were conducted in microcosms consisting of algae, bacteria, crustaceans, and fish embryos. Each microcosm was exposed to one of five surface chemistries within each shape profile (at 0, 0.1, or 0.5 mg Ag/L) to investigate the role of shape and surface composition on organismal uptake and toxicity. The hybrid lipid-coated AgNPs did not result in any significant release of Ag+ and had the most significant toxicity to D. magna, the most sensitive species, although the bacterial population growth rate was reduced in all exposures. Despite AgNPs resulting in increasing algal growth over the experiment, we found no correlation between algal growth and the survival of D. magna, suggesting that the impacts of the AgNPs on bacterial survival influenced algal growth rates. No significant impacts on zebrafish embryos were noted in any exposure. Our results demonstrate that the size, shape, and surface chemistry of AgNPs can be engineered to achieve specific goals while mitigating nanoparticle risks.

Green Synthesis Silver Nanoparticles Using Sembung (Blumea balsamifera) Leaf Extract as an Antibacterial and Antioxidant

Silver Nanoparticles essentially focuses on the synthesis of nano-sized particles produced through chemical, physical and biological processes, which contribute significantly to the control of plant and animal diseases and have shown considerable promise in improving the quality of living conditions and human health. Currently, silver nanoparticles (AgNP) have shown their potential as an alternative antibacterial and antioxidant agent in many studies. The method for making silver nanoparticles, namely Green synthesis, involves the use of plants for the synthesis process of various types of nanoparticles. Green synthesis has the advantages, namely that the method is simple, environmentally friendly, non-polluting, antitoxic and cost-effective. The aim of this research is to determine the antibacterial and antioxidant activity of AgNPs. In this research, the nanoparticle solution was visually determined by the yellow-brown color change. In the spectrophotometer absorption spectrum appears at a wavelength of 425 nm. The results of determining the size distribution of silver nanoparticles using PSA show that the particle size distribution obtained has an average value of 40.5 nm and 59.6 nm for silver nanoparticles for AgNO3 concentrations of 1 mM and 2 mM, respectively. FTIR measurements are used to determine the presence of bioactive molecules that may be responsible for the stabilization that acts as a capping agent. Absorption spiked at 3.280; 2.919; 1.583; 1.379; 1.239 and 1.068 cm−1 were determined for sembung leaf extract, while silver nanoparticles showed an absorption spike at 3.368; 2.850; 1.594; 1.369; 1.244 and 1.108 cm−1. The results of XRD analysis of AgNP show that it has been successfully synthesized which can be seen from the formation of a narrow peak indicating the crystalline nature of the nanoparticles formed. The results of TEM analysis of AgNPs in this study are mixed shapes such as spherical, hexagonal and triangular shapes of silver nanoparticles. The antibacterial activity test of silver nanoparticles with sembung leaf extract with varying concentrations of AgNO3 solution was successful as indicated by the formation of an inhibition zone for Eschericia coli and Staphylococcus aureus bacteria. The results show that the antioxidant activity of AgNPs shows that the percentage of inhibition increases as the concentration of AgNPs increases from 100 to 500 ppm and ascorbic acid increases from 1 to 5 ppm.

Development of ecofriendly and sustainable bioplastics from cassava starch: Tailoring the properties using nanoparticles

In an era marked by growing environmental concerns and the need for sustainable living, the development of environmentally friendly and biodegradable products has become paramount. This work proposes the preparation of eco-friendly and sustainable value-added products like carry bags and garbage bags from cassava starch. A cassava starch: plasticizer ratio of 1:0.05 has been optimized to prepare bioplastics with good mechanical properties. We have used nearly spherical shaped silver nanoparticles ranging between a particle size of 9–15 nm and spherical zinc oxide nanoparticles ranging between 12 and 38 nm prepared by green methods which were characterized using XRD, SEM and TEM. Using the optimum cassava starch:plasticizer ratio, two sets of bioplastics were prepared-one containing varying amounts of silver nanoparticles and the other with varying amounts of zinc oxide nanoparticles. For both types of bioplastics, 1% nanoparticle addition gave maximum tensile strength of 4.8037 N/mm2 for zinc oxide incorporated bioplastics and 4.3320 N/mm2 for silver incorporated bioplastics. The addition of nanoparticles did not much change the thermal stability of bioplastics. Soil, air and water degradation studies were done for 31 days. The rate of soil degradation increased on nanoparticle addition. The durability of the bioplastics was confirmed during air degradation studies. The nanoparticle incorporated samples showed lesser degradation in air and water. Thus, addition of nanoparticles customizes the properties of bioplastics, making them suitable substitutes for traditional plastics in a wide range of uses.

The Shape Modulation of Laser-Induced Nanowelded Microstructures Using Two Colors

The light-based nanowelding of metallic nanoparticles is of particular interest because it provides convenient and controlled means for the conversion of nanoparticles into microstructures and the fabrication of nanodevices. In this study, we investigated the wavelength dependence of laser-induced nanowelded shapes of silver nanoparticles (AgNPs). We observed that the nanowelded microstructures illuminated with only a 405 nm laser were more branched than those formed via illumination using both the 405 nm and 532 nm lasers. We quantified this observation by two compactness descriptors and examined the dependence of the power of the 532 nm laser. More importantly, to understand the experimental observations, we formulated and tested a hypothesis by calculating the wavelength-dependent electric field enhancement due to the surface plasmon resonance of the AgNPs and nanowelded microstructures when illuminated with lights at the two wavelengths. Based on the different patterns of hot spots for welding AgNPs from these calculations, numerical simulations successfully reproduced the different shapes of nanowelded microstructures, supporting our hypothesis. This work suggests the possibility of light-based control of the shapes of laser-induced nanowelded microstructures of metallic nanoparticles. This work is expected to facilitate the development of broader applications using the nanowelding of metallic nanoparticles.

Enhanced nonlinear optical absorption and optical limiting performance of nanoparticles embedded lanthanum alkali borate glasses bearing holmium ions at off–resonant spectral excitation

Herein, the efficacy of silver nanoparticles on the nonlinear optical features of holmium ions bearing melt–quenched borate–based glasses has been investigated. The silver nanoparticles free holmium doped glass possesses weak nonlinear absorption and high optical limiting threshold in the near–infrared spectral range. It was observed that the nonlinear absorption and optical limiting performance were significantly improved upon co–doping of silver NPs in the lanthanum alkali borate glasses. The linear optical absorption measurements partially confirmed the presence of silver nanoparticles in the prepared glasses. The electron microscopic measurements disclosed the evidence for the formation of spherically shaped silver nanoparticles in the glasses. The nonlinear optical and optical limiting features were ascertained by the open aperture Z–scan technique in off–plasmon excitations by benefitting femtosecond laser pulses fired at kHz repetition rate. The outcomes endorse that the high AgCl loaded lanthanum alkali borate glasses are useful in suppressing the high energy near–infrared laser radiation for the protection of sensitive optical devices (e.g., human eye) from the laser damage.

Construction of silver-coated high translucent zirconia implanting abutment material and its property of antibacterial

High translucent zirconia (HTZ) has excellent mechanical properties, biocompatibility, and good semi-translucency making it an ideal material for aesthetic anterior dental implant abutments without antibacterial properties. In the oral environment, the surface of the abutment material is susceptible to microbial adhesion and biofilm formation, which can lead to infection or peri-implantitis and even implant failure. This study aims to promote the formation of a biological seal at the implant-soft tissue interface by modifying the HTZ surface, using the load-bearing capacity of the aluminosilicate porous structure and the broad-spectrum antibacterial effect of silver nanoparticles to prevent peri-implant bacterial infection and inflammation and to improve the success rate and prolong the use of the implant. FE-SEM (field emission scanning electron microscopes), EDS (energy dispersive spectroscopy), and XPS (X-ray photoelectron spectroscopy) results showed that aluminosilicate non-vacuum sintering can form open micro- and nanoporous structures on HTZ surfaces, and that porous aluminosilicate coatings obtain a larger number, smaller size, and more uniformly shaped silver nanoparticles than smooth aluminosilicate coatings, and could be deposited deeper in the coating. The ICP-AES (inductively coupled plasma-atomic emission spectroscopy) results showed that the early silver ion release of both the smooth silver coating and the porous silver coating was obvious, the silver ion concentration released by the former was higher than that of the latter. However, the silver ion concentration released by the porous silver coating was higher than that of the smooth coating when the release slowed down. Both smooth and porous silver coatings both inhibited E. coli (Escherichia coli), S. aureus (Staphylococcus aureus), and L. acidophilus (L. acidophilus), and porous silver coatings had stronger antibacterial properties. The silver coating was successfully constructed on the surface of HTZ, through aluminium silicate sintering and silver nitrate solution impregnation. It was found that the high concentration environment of silver nitrate solution was more advantageous for nano-Ag deposition, and the non-vacuum sintered porous surface was able to obtain a larger number of nano-Ag particles with smaller sizes. The porous Ag coating exhibited superior antibacterial properties. It was suggested that the HTZ with silver coating had clinical application, and good antibacterial properties that can improve the survival rate and service life of implants.

Particle-Driven Effects at the Bacteria Interface: A Nanosilver Investigation of Particle Shape and Dose Metric.

Design criteria for controlling engineered nanomaterial (ENM) antimicrobial performance will enable advances in medical, food production, processing and preservation, and water treatment applications. In pursuit of this goal, better resolution of how specific ENM properties, such as nanoparticle shape, influence antimicrobial activity is needed. This study probes the antimicrobial activity toward a model Gram-negative bacterium, Escherichia coli (E. coli), that results from interfacial interactions with differently shaped silver nanoparticles (AgNPs): cube-, disc-, and pseudospherical-AgNPs. The EC50 value (i.e., the concentration of AgNPs that inactivates 50% of the microbial population) for each shape is identified and presented as a function of mass, surface area, and particle number. Further, shifts in relative potency are identified from the associated dose-response curves (e.g., shifts left, to lower concentrations, indicate greater potency). When using a mass-based dose metric, the disc-AgNPs present the highest antimicrobial activity of the three shapes (EC50: 2.39 ± 0.26 μg/mL for discs, 2.99 ± 0.96 μg/mL for cubes, 116.33 ± 6.43 μg/mL for pseudospheres). When surface area and particle number are used as dose metrics, the cube-AgNPs possess the highest antimicrobial activity (EC50-surface area: 4.70 × 10-5 ± 1.51 × 10-5 m2/mL, EC50-particle: 5.97 × 109 ± 1.92 × 109 particles/mL), such that the relative trend in potency becomes cubes > discs > pseudospheres and cubes ≫ discs ⩾ pseudospheres, respectively. The results reveal that the antimicrobial potency of disc-AgNPs is sensitive to the dose metric, significantly decreasing in potency (∼5-30×) upon conversion from a mass-based concentration to surface area and particle number and influencing the conclusions drawn. The shift in relative particle potency highlights the importance of investigating various dose metrics within the experimental design and signals different particle parameters influencing shape-based antimicrobial activity. To probe shape-dependent behavior, we use a unique empirical approach where the physical and chemical properties (ligand chemistry, surface charge) of the AgNP shapes are carefully controlled, and total available surface area is equivalent across shapes as made through modifications to particle size and concentration. The results herein suggest that surface area alone does not drive antimicrobial activity as the different AgNP shapes at equivalent particle surface area yield significantly different magnitudes of antimicrobial activity (i.e., 100% inactivation for cube-AgNPs, <25% inactivation for disc- and pseudospherical-AgNPs). Further, the particle shapes studied possess different crystal facets, illuminating their potential influence on differentiating interactions between the particle surface and the microbe. Whereas surface area may partly contribute to antimicrobial activity in certain ENM shapes (i.e., disc-AgNPs in relation to the pseudospherical-AgNPs), the different magnitudes of antimicrobial activity across shape provide insight into the likely role of other particle-specific factors, such as crystal facets, driving the antimicrobial activity of other shapes (i.e., cube-AgNPs).

Shape Dependence of Silver-Nanoparticle-Mediated Synthesis of Gold Nanoclusters with Small Molecules as Capping Ligands.

In this study, differently shaped silver nanoparticles used for the synthesis of gold nanoclusters with small capping ligands were demonstrated. Silver nanoparticles provide a reaction platform that plays dual roles in the formation of Au NCs. One is to reduce gold ions and the other is to attract capping ligands to the surface of nanoparticles. The binding of capping ligands to the AgNP surface creates a restricted space on the surface while gold ions are being reduced by the particles. Four different shapes of AgNPs were prepared and used to examine whether or not this approach is dependent on the morphology of AgNPs. Quasi-spherical AgNPs and silver nanoplates showed excellent results when they were used to synthesize Au NCs. Spherical AgNPs and triangular nanoplates exhibited limited synthesis of Au NCs. TEM images demonstrated that Au NCs were transiently assembled on the surface of silver nanoparticles in the method. The formation of Au NCs was observed on the whole surface of the QS-AgNPs if the synthesis of Au NCs was mediated by QS-AgNPs. In contrast, formation of Au NCs was only observed on the edges and corners of AgNPts if the synthesis of Au NCs was mediated by AgNPts. All of the synthesized Au NCs emitted bright red fluorescence under UV-box irradiation. The synthesized Au NCs displayed similar fluorescent properties, including quantum yields and excitation and emission wavelengths.

Enhanced thermal conductivity in Ag-H2O nanofluids by nanoparticles of different shapes: Insights from molecular dynamics simulation

The mechanism of thermal conductivity enhancements and influential factors make a lot of sense in the intensive investigation of nanofluids. While numerous studies have explored the effect of solid–liquid interfacial layers on thermal conductivity improvement in water-based nanofluids with diverse applications, investigations into the intrinsic mechanisms underlying interfacial layers in relation to nanoparticle shape remain limited. The thermal conductivity of water-based Ag-H2O nanofluids was investigated using molecular dynamics simulations of non-equilibrium molecular dynamics (NEMD), with emphasis placed on the shape and volume fraction of nanoparticles. The influence of nanofluid volume fraction on thermal conductivity was revealed through visual analysis of 3D smoothed surface plots, highlighting the positive correlation between thermal properties and increasing volume fraction of nanoparticles. Moreover, the contribution of different shapes of silver nanoparticles to thermal conductivity enhancement demonstrated an increasing trend with the corresponding growth in surface-to-volume ratio (S/V values associated with different particle shapes). For the volume fraction of 1.5%, the minimum thermal conductivity enhancement of 22.75% was observed for the spherical shape, while the maximum thermal conductivity enhancement of 25.51% was achieved with the triple-platelet particles. Importantly, the comprehensive analysis of radial distribution function (RDF) and mean square displacement (MSD) indicated the positive effect of interfacial nanolayers influenced by nanoparticles of various shapes on the thermal conductivity of nanofluids. This study provides valuable insights into the impact of nanoparticle shape on the thermal properties of nanofluids, opening up promising prospects for future molecular dynamics simulations.

Rapid photodegradation of toxic organic compounds and photo inhibition of bacteria in the presence of novel hydrothermally synthesized Ag/Mn–ZnO nanomaterial

Purified water is the most concerning issue these days, and utmost conventional practices are allied with various downsides. Therefore, an ecologically benign and easily amicable therapeutic approach is the requirement. In this wonder, nanometer phenomena bring an innovative change to the material world. It has the potential to produce nanosized materials for wide-ranging applications. The subsequent research highlights the synthesis of Ag/Mn–ZnO nanomaterial via a one-pot hydrothermal route with an efficient photocatalytic activity against organic dyes and bacteria. The outcomes revealed that the size of the particle (4–5 nm) and dispersion of spherically shaped silver nanoparticles intensely affected by employing Mn–ZnO as a support material. Use of silver NPs as a dopant activates the active sites of the support medium and provides a higher surface area to upsurge the degradation rate. The synthesized nanomaterial was evaluated against photocatalytic activity using Methyl orange and alizarin red as model dyes and confided that more than 70% of both the dyes degraded under 100 min duration. It is well recognize that the modified nanomaterial recreates an essential role in every light-based reaction, and virtually produced highly reactive oxygen species. The synthesized nanomaterial was also evaluated against E. coli bacterium both in light and dark. The zone of inhibition in the presence of Ag/Mn–ZnO was observed both in light (18 ± 0.2 mm) and dark (12 ± 0.4 mm). The hemolytic activity shows that Ag/Mn–ZnO has very low toxicity. Hence, the prepared Ag/Mn–ZnO nanomaterial might be an effective tool against the depletion of further harmful environmental pollutants and microbes.

The effect of particle shape on flow and heat transfer of Ag-nanofluid along stretching surface

The primary objective of the present work is to examine the axisymmetric flow and heat transfer over an unsteady radially stretching surface for different shapes of silver (Ag) nanoparticles. Due to their remarkable electrical conductivity and chemical stability for a variety of applications, silver nanoparticles are attracting attention. So, we consider five different shapes of silver nanoparticles. By using suitable transformation energy and momentum equations are transformed into nonlinear ordinary differential equations. The dimensionless equations are solved by BVP4C technique to get numerical results for the modeled problem. For velocity, temperature, skin friction coefficient, and Nusselt number, numerical values are obtained using and are also graphically displayed. Comprehensive discussion is given on the effects of many factors, including solid volume fraction, Prandtl number, unsteadiness parameter, magnetic parameter, slip parameter, and Eckert number. For both velocity and temperature Platelet shapes nanoparticles shows maximum flow and heat transfer. Sphere shape nanoparticles possess the highest skin friction coefficients values and lowest value of Nusselt number.

Stability of Silver Nano Particles in Deionized Water Produced by using the Low-Energy Nd : YAG laser

Nanoparticle stability is essential for its usage in a wide range of fields, including healthcare. Therefore, the purpose of this study is to evaluate the safety of silver nanoparticles in deionized (DI) water using low-energy laser ablation. In this research, a Nd: YAG laser (Q-smart 850 by Quantel) was utilized to produce radiation at 1064 nm and 50 mJ of energy. 10 minutes were spent blasting deionized water full of colloidal silver nanoparticles at a frequency of 10 Hz (DI water). After 30 days, the photos demonstrate that the color of the colloidal SNPs has changed to be more transparent, and no agglomeration or precipitation has taken place. The little impact of Brownian motion and the evenly distributed population of SNPs contribute to their stability. Because the nanoparticles in the colloid were slightly diluted, the absorbance dropped. When subjected to a low-energy laser, they maintain their spherical shape. Colloidal silver nanoparticles have a golden yellow hue. There has been no variation in the colloidal SNPs after 30 days. Spectral analysis of colloidal silver nanoparticles reveals an SPR peak at 403 nm. The average size of silver NPs was measured to be 28 nm using the ImageJ software. The shape of silver nanoparticles is typically spherical.

Saturable absorption and negative nonlinear refraction index evolution in silver nanoparticles colloids

In this paper, silver nanoparticles colloids in deionized water with evolution from spherical to disk and decahedral shapes, and average size between ∼10–50 nm, were synthesized controlling the reaction conditions. The samples were irradiated using a cool-white light-emitting diode source for several hours, which allowed the tailoring of the position of the surface plasmon resonance from 408 nm to 495 nm. The nonlinear optical properties of silver nanoparticles colloids were investigated by the Z-scan technique and femtosecond laser pulses @ 800 nm. The nonlinear absorption obtained by an open aperture Z-scan setup showed a saturable absorption effect, while the nonlinear refraction index measured by a close aperture setup revealed a negative lens-like (self-defocusing) behavior in all samples. Measured effective nonlinear absorption ranged from −5.26×10−9 to −1.03×10−9 cm/W, while nonlinear refractive index was −2.47×10−13 to −1.48×10−13 cm2/W. We found that as the silver nanoparticles shape is modified from quasi-spherical to disk and decahedral, and its size is increased, the linear absorption and the absolute values of the effective nonlinear absorption and nonlinear refractive index decreased. We also found that the nonlinear optical response is more sensitive to size and morphology than the linear optical response.

Rapid Detection of Mercury Ions Using Sustainable Natural Gum-Based Silver Nanoparticles

Fabrication of metal nanostructures using natural products has attracted scientists and researchers due to its renewable and environmentally benign availability. This work has prepared an eco-friendly, low-cost, and rapid colorimetric sensor of silver nanoparticles using tree gum as a reducing and stabilizing agent. Several characterization techniques have been exploited to describe the synthesized nanosensor morphology and optical properties. Ultraviolet−Visible (UV−Vis) spectroscopy has been used for monitoring the localized plasmon surface area. High-resolution transmission electron microscopy (HR-TEM) illustrated the size and shape of silver nanoparticles. X-ray diffraction spectra showed the crystallography and purity of the product. Silver nanoparticles decorated with almond gum molecules (AgNPs@AG) demonstrated high sensitivity and colorimetric detection of mercury ions in water samples. The method is based on the aggregation of AgNPs and the disappearing yellow color of AgNPs via a spectrophotometer. The detection limit of this method was reported to be 0.5 mg/L. This work aimed to synthesize a rapid, easy-preparation, eco-friendly, and efficient naked-eye colorimetric sensor to detect toxic pollutants in aqueous samples.

In Vitro Antibacterial Activity of Green Synthesized Silver Nanoparticles Using Azadirachta indica Aqueous Leaf Extract against MDR Pathogens.

Rice is the most important staple food crop feeding more than 50% of the world's population. Rice blast is the most devastating fungal disease, caused by Magnaporthe oryzae (M. oryzae) which is widespread in rice growing fields causing a significant reduction in the yield. The present study was initiated to evaluate the effect of green synthesized silver nanoparticles (AgNPs) on the biochemical constituents of rice plants infected with blast. AgNPs were synthesized by using Azadirachta indica leaf extract and their characterization was performed using UV-visible spectroscopy, particle size analyser (PSA), scanning electron microscope (SEM), and X-ray diffraction (XRD) which confirmed the presence of crystalline, spherical shaped silver nanoparticles with an average size of 58.9 nm. After 45 days of sowing, artificial inoculation of rice blast disease was performed. After the onset of disease symptoms, the plants were treated with AgNPs with different concentrations. Application of nanoparticles elevated the activity of antioxidative enzymes such as superoxide dismutase, catalase, peroxidase, glutathione reductase, and phenylalanine ammonia-lyase compared to control plants, and total phenol and reducing sugars were also elevated. The outcome of this study showed that an increase in all biochemical constituents was recorded for A. indica silver nanoparticles-treated plants. The highest values were recorded in 30 ppm and 50 ppm AgNPs-treated plants, which showed the highest resistance towards the pathogen. Green synthesized AgNPs can be used in future for disease control in susceptible varieties of rice. The synthesized AgNPs using A. indica leaf extract have shown promising antibacterial activity when tested against 14 multidrug-resistant (MDR) bacteria comprising Gram-negative bacteria Escherichia coli (n = 6) and Klebsiella pneumoniae (n = 7) with a good zone of inhibition diameter, tested with the disc diffusion method. Based on these findings, it appears that A. indica AgNPs have promise as an antibacterial agent effective against MDR pathogens.

“The Effects of Silver Nanoparticle Shape on Protein Adsorption and Neural Stem Cell Viability”

Silver nanoparticles (AgNPs) are important and widely used as antimicrobials and nanodrug carriers. The increased use of AgNPs in consumer products has raised concerns about nanosafety; for instance, AgNPs may be inhaled and translocated to the brain via olfactory neural stem cells/progenitors. While the biological effects of nanoparticle size have been widely investigated, there are little data on the effects of particle shape on cellular phenotype. Therefore, here we investigated the interactions between AgNP spheres, rods, cubes, and triangles and human plasma proteins as well as their effects on the viability of NE-4C neural stem cells. Nanoparticles were synthesized by wet chemistry methods and characterized by UV-vis spectroscopy, dynamic light scattering, zeta potential measurement, transmission electron microscopy, nanoparticle tracking analysis, and differential centrifugal sedimentation. NE-4C cell viability was assessed using the MTT reduction assay, and the cellular uptake of differently shaped nanoparticles was monitored by electron microscopy. All 50 nm (in at least one dimension) AgNPs exerted toxic effects, with rods and cubes displaying greater toxicity than spheres and triangles. These cellular and physicochemical results indicate that edges on the AgNPs increase toxicity, presumably due to enhanced ion dissolution from the edges.

Influence of Reagents on the Synthesis Process and Shape of Silver Nanoparticles.

The aim of this study was to prepare the silver nanoparticles (AgNPs) via chemical reduction and analyze the impact of used reduction agents: sodium borohydride (NaBH4), trisodium citrate (TSC), polyvinylpyrrolidone (PVP), and hydrogen peroxide (H2O2) on the reduction rate of Ag+ ions to Ag0, and on nanoparticles shape. It was proven that combinations of reduction agents dramatically influence the synthesis rate of AgNPs and the color of solutions, which depends on the shape and size of nanoparticles. NaBH4, TSC, and PVP showed good reduction power. In particular, TSC proved to be a key factor influencing the shape of AgNPs. The shape of nanoparticles influences the color of colloidal solutions. Yellow solutions, where UV-vis absorbance maxima (ABSmax) are in the wavelength interval 380–420 nm, contain spherical particles with a mean size of 25 nm, whereas the blue shift of ABSmax to wavelengths higher than 750 nm indicate the presence of triangular nanoparticles (size interval 18–150 nm). A mixture of spherical, triangular, irregular, and hexagonal nanoparticles give different color, e.g., green. The formation and stability of AgNPs was tracked by UV-vis spectroscopy, size and shape by TEM techniques, and particle size distribution was studied by particle size analyzer.

MICROWAVE-ASSISTED GREEN SYNTHESIS OF SILVER NANOPARTICLES USING EXTRACT OF SPONDIAS PINNATA BARK

Formation of silver nanoparticles with irradiation of microwaves using biological agents such as plant extracts is one of the eco-friendly green synthesis approaches which is economical in comparison with the physical and chemical methods. This study is focused at preparation of silver nanoparticles silver using Spondias pinnata bark extract by microwave irradiation and its comparison with aging method. Formation of silver nanoparticles was identified by observing the surface plasmon resonance absorption band peak at ~432 nm by UV-visible spectrophotometer. Optimization of the synthesis procedure was carried out using different amount of extract, concentration of substrate and microwave irradiation time and morphological features were characterised. A solution containing 8ml plant extract and 8 mM silver nitrate exposed to 90 sec microwave irradiation time was identified as optimised condition for the production of spherical shaped silver nanoparticles with a size of 34.52 nm which indicates that faster formation of silver nanoparticles compared to the aging method. Present research shows the importance of optimization of bio reduction conditions and the amount of reactants required for regulation of the morphology of silver nanoparticles as well as to obtain homogenous solution which is the main problem encountered in plant- mediated production of silver nanoparticles.

Use of field-flow fractionation and single particle inductively coupled plasma mass spectrometry for the study of silver nanoparticle shape transformation

Field-flow fractionation-inductively coupled plasma mass spectrometry (FFF-ICP-MS) and single particle ICP-MS (SP-ICP-MS) were used for investigation of silver nanoparticle shape transformation. Commercial and laboratory synthesized silver nanoparticles were employed in this study. For laboratory synthesized silver nanoparticles, silver nanosphere seed was first prepared by reducing silver nitrate with sodium borohydride in starch stabilizing agent. The obtained nanosphere exhibited 27.5 nm hydrodynamic diameter from FFF-ICP-MS analysis with equivalent spherical diameter of 26 nm from SP-ICP-MS analysis. This nanosphere underwent shape transformation induced by varying volumes of hydrogen peroxide. Increasing hydrogen peroxide volume resulted in increased particle diameter, and nanoplate formation. These synthesized nanoparticles and commercial silver nanoplates were subjected to shape transformation induced by bromide etching. General trend was observed that bromide addition caused particles to become smaller. Clear trend was found for commercial silver nanoplates that bromide addition caused both hydrodynamic diameter measured by FFF-ICP-MS and equivalent spherical diameter measured by SP-ICP-MS become smaller. Furthermore, the combined information from FFF-ICP-MS and SP-ICP-MS analysis with the use of TEM data were proposed to provide additional information on the edge length and the thickness of silver nanoplates. With the known edge length of commercial silver nanoplates, the thickness was estimated to be 25.4 nm, 7.64 nm, and 4.95 nm for triangular nanoplates with the edge length of 32 nm, 70 nm, and 153.1 nm, respectively. Both FFF-ICP-MS and SP-ICP-MS provided unique information which are useful for nanoparticle characterization.