Commercial AgNPs Research Articles

Synthesis and characterization of nanosilver with antibacterial properties using Pinus densiflora young cone extract

This study describes an eco-friendly, rapid method for green synthesis of silver nanoparticles (Ag NPs) from an aqueous solution of silver nitrate using Pinus densiflora for. multicaulis Uyeki young cone extract in a single-pot process. Color changes, ultraviolet–visible spectra (444.5nm), X-ray diffraction peaks (2θ=39.68, 46.92, 68.12, and 79.10), and Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of Ag NPs and phytochemicals. Transmission electron microscopy showed that the nanoparticles were mostly oval in shape, with a few triangular-shaped particles. Average particle size was 30–80nm. Phytochemicals present in the young pine cone extract were likely responsible for the reduction of Ag+ ions. The synthesized Ag NPs (40μg) had a 7mm larger zone of inhibition against the skin pathogen Brevibacterium linens than commercial Ag NPs, Propionibacterium acnes (14mm), Bacillus cereus (9mm) and Staphylococcus epidermidis (10mm).

Phytosynthesis of silver nanoparticles by Prunus yedoensis leaf extract and their antimicrobial activity

Green synthesis of silver nanoparticles (Ag NPs) using Prunus×yedoensis leaf extract was studied. Color changes, ultraviolet–visible spectra (436nm), X-ray diffraction peaks (2θ=39.26, 45.54, 65.12, and 79.21) and Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of Ag NPs. Transmission electron microscopy shows that the nanoparticles are mostly spherical and oval in shape, with an average particle size of 20 to 70nm. The phytoconstituents present in the leaf extract could be responsible for the reduction of Ag+ ions. The synthesized Ag NPs (30μg) show a 18 and 20mm zone of inhibition against skin pathogens Propionibacterium acnes and Staphylococcus epidermidis compared with commercial Ag NPs.

Antimicrobial fabrication of cotton fabric and leather using green-synthesized nanosilver

This study aims to investigate the green synthesis of silver nanoparticles (AgNPs) by Erigeron annuus (L.) pers flower extract as reducing and capping agent, and evaluation of their antibacterial activities for the first time. The obtained product was confirmed by UV–Vis spectrum, high resolution-transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction studies. The optimum AgNPs production was achieved at pH 7, metal silver (Ag+ ion) concentration of 2.0mM, flower extract concentration 4%, and time 335min. In addition, the antibacterial activity of cotton fabrics and tanned leather loaded with AgNPs, commercial AgNPs, flower extract, Ag+ ion and blend of flower extract with AgNPs were evaluated against Gram-positive odor causing bacteria Brevibacterium linens and Staphylococcus epidermidis. The results showed maximum zone of inhibition (ZOI) by the cotton fabrics embedded with blend of flower extract and AgNPs against B. linens. The structure and morphology of cotton fabric and leather samples embedded with AgNPs, Ag+ ion and blend of flower extract with AgNPs were examined under field emission scanning electron microscope.

A disposable sticky electrode for the detection of commercial silver NPs in seawater

The ability to perform efficient and affordable field detection and quantification of nanoparticles in aquatic environmental systems remains a significant technical challenge. Recently we reported a proof of concept of using ‘sticky’ electrodes for the detection of silver nanoparticles (Tschulik et al 2013 Nanotechnology 29 295502). Now a disposable electrode for detection and quantification of commercial Ag nanoparticles in natural seawater is presented. A disposable screen printed electrode is modified with cysteine and characterized by sticking and stripping experiments, with silver nanoparticle immobilization on the electrode surface and subsequent oxidative stripping, yielding a quantitative determination of the amount of Ag nanoparticles adhering to the electrode surface. The modified electrode was applied to natural seawater to mimic field-based environmental monitoring of Ag NPs present in seawater. The results demonstrated that commercial Ag NPs in natural seawater can be immobilized, enriched and quantified within short time period using the disposable electrodes without any need for elaborate experiments.

Carbon supported Ag nanoparticles with different particle size as cathode catalysts for anion exchange membrane direct glycerol fuel cells

The effect of Ag particle size on oxygen reduction reaction (ORR) at the cathode was investigated in anion exchange membrane direct glycerol fuel cells (AEM-DGFC) with oxygen as an oxidant. At the anode, high purity glycerol (99.8 wt%) or crude glycerol (88 wt%, from soybean biodiesel) was used as fuel, and commercial Pt/C served as the anode catalyst. A solution phase-based nanocapsule synthesis method was successfully developed to prepare the non-precious Ag/C cathode catalyst, with LiBEt3H as a reducing agent. XRD and TEM characterizations show that as-synthesized Ag nanoparticles (NP) with a size of 2–9 nm are well dispersed on the Vulcan XC-72 carbon black support. Commercial Ag nanoparticles with a size of 20–40 nm were also supported on carbon black as a control sample. The results show that higher peak power density was obtained in AEM-DGFC employing an Ag-NP catalyst with smaller particle size: nanocapsule made Ag-NP > commercial Ag-NP (Alfa Aesar, 99.9%). With the nanocapsule Ag-NP cathode catalyst, the peak power density and open circuit voltage (OCV) of AEM-DGFC with high-purity glycerol at 80 °C are 86 mW cm−2 and 0.73 V, respectively. These are much higher than 45 mW cm−2 and 0.68 V for the AEM-DGFC with the commercial Ag/C cathode catalyst, which can be attributed to the enhanced kinetics and reduced internal resistance. Directly fed with crude glycerol, the AEM-DGFC with the nanocapsule Ag-NP cathode catalyst shows an encouraging peak power density of 66 mW cm−2, which shows great potential of direct use of biodiesel waste fuel for electricity generation.

Regulation of sodium and calcium inDaphnia magnaexposed to silver nanoparticles

The toxicity of manufactured silver nanoparticles (AgNPs) has been widely studied, but the influence of AgNPs on the major ions (such as sodium [Na] and calcium [Ca]) regulations are unknown. In the present study, a freshwater cladoceran Daphnia magna was exposed to commercial AgNPs coated with polyvinylpyrrolidone. After 48 h, the Na body content was significantly reduced by AgNO3 exposure, but the Ca body content was significantly increased under AgNO3 and AgNP exposures, respectively. No effect was observed on the body concentrations of Na and Ca at 50 to 500 µg/L AgNPs with 1-µM cysteine addition. Exposure of AgNO3 and AgNPs inhibited the Na influx and elevated the Na efflux. In contrast, their exposure increased the Ca influx, but did not affect the Ca efflux. The results of the present study demonstrated the significant influences of AgNO3 and AgNPs (without cysteine) on Na and Ca regulations. Such effect of AgNPs on Na and Ca regulation disappeared after cysteine addition, indicating that the soluble Ag released from AgNPs played a major role in the ionoregulatory dysfunction.

Silver Nanoparticle Exposure Attenuates the Viability of Rat Cerebellum Granule Cells through Apoptosis Coupled to Oxidative Stress

The impact of silver nanoparticles (AgNPs) on the central nervous system is a topic with mounting interest and concern and the facts remain elusive. In the current study, the neurotoxicity of commercial AgNPs to rat cerebellum granule cells (CGCs) and the corresponding molecular mechanism are closely investigated. It is demonstrated that AgNPs induce significant cellular toxicity to CGCs in a dose-dependent manner without damaging the cell membrane. Flow cytometry analysis with the Annexin V/propidium iodide (PI) staining indicates that the apoptotic proportion of CGCs upon treatment with AgNPs is greatly increased compared to the negative control. Moreover, the activity of caspase-3 is largely elevated in AgNP-treated cells compared to the negative control. AgNPs are demonstrated to induce oxidative stress, reflected by the massive generation of reactive oxygen species (ROS), the depletion of antioxidant glutathione (GSH), and the increase of intracellular calcium. Histological examination suggests that AgNPs provoke destruction of the cerebellum granular layer in rats with concomitant activation of caspase-3, in parallel to the neurotoxicity of AgNPs observed in vitro. Taken together, it is demonstrated for the first time that AgNPs substantially impair the survival of primary neuronal cells through apoptosis coupled to oxidative stress, depending on the caspase activation-mediated signaling.

Influence of pH on the transport of silver nanoparticles in saturated porous media: laboratory experiments and modeling

Given the ubiquity of silver nanoparticles (AgNPs) and their potential for toxic effects on both humans and the environment, it is important to understand their environmental fate and transport. The purpose of this study is to gain information on the transport properties of commercial AgNP suspensions in a glass bead-packed column under saturated flow conditions at different solution pH levels. Commercial AgNPs were characterized using high-resolution transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. Transport data were collected at different pH levels (4, 6.5, 9, and 11) at fixed ionic strength. Capture of AgNPs increased as the pH of the solution increased from 4 to 6.5. Further increase in pH to 9 and 11 decreased the attachment of AgNPs to the glass beads. AgNP concentration versus time breakthrough data were simulated using an advection–dispersion model incorporating both irreversible and reversible attachment. In particular, a reversible attachment model is required to simulate breakthrough curve tailing at near neutral pH, when attachment is most significant. The laboratory and modeling study reveals that for natural groundwaters, AgNP transport in porous media may be retarded due to capture; but ultimately, most of the mass may be slowly released over time.

Silver Nanoparticles Disrupt Wheat (Triticum aestivum L.) Growth in a Sand Matrix

Hydroponic plant growth studies indicate that silver nanoparticles (Ag NPs) are phytotoxic. In this work, the phytotoxicity of commercial Ag NPs (10 nm) was evaluated in a sand growth matrix. Both NPs and soluble Ag were recovered from water extracts of the sand after growth of plants challenged with the commercial product; the surface charge of the Ag NPs in this extract was slightly reduced compared to the stock NPs. The Ag NPs reduced the length of shoots and roots of wheat in a dose-dependent manner. Furthermore, 2.5 mg/kg of the NPs increased branching in the roots of wheat (Triticum aestivum L.), thereby affecting plant biomass. Micron-sized (bulk) Ag particles (2.5 mg/kg) as well as Ag ions (63 μg Ag/kg) equivalent to the amount of soluble Ag in planted sand with Ag NPs (2.5 mg/kg) did not affect plant growth compared to control. In contrast, higher levels of Ag ions (2.5 mg/kg) reduced plant growth to a similar extent as the Ag NPs. Accumulation of Ag was detected in the shoots, indicating an uptake and transport of the metal from the Ag NPs in the sand. Transmision electron microscopy indicated that Ag NPs were present in shoots of plants with roots exposed to the Ag NPs or high levels of Ag ions. Both of these treatments caused oxidative stress in roots, as indicated by accumulation of oxidized glutathione, and induced expression of a gene encoding a metallothionein involved in detoxification by metal ion sequestration. Our findings demonstrate the potential effects of environmental contamination by Ag NPs on the metabolism and growth of food crops in a solid matrix.

Size-Dependent Uptake of Silver Nanoparticles in Daphnia magna

The toxicity of silver nanoparticles (AgNPs) has been widely investigated, but the process of bioaccumulation such as uptake remains less studied. In the present study, we employed the radioisotope ((110m)Ag) to trace the behaviors of commercial AgNPs with three nominal particle sizes (20, 50, and 100 nm) and two surface coatings (citrate and tannic acid) in a model organism Daphnia magna . The size distributions of AgNPs in the medium increased continuously as the exposure time increased, especially for the smallest AgNPs (20 nm). Cysteine, the amino acid containing thiol group, significantly enhanced particle aggregation, with a 30-fold increase of the hydrodynamic size for AgNPs with 20 nm nominal size after 6 h of exposure. We demonstrated that the influx rates of AgNPs into daphnids were size-dependent. At 500 μg/L AgNPs with 1 μM cysteine, the influx rates of AgNPs were in the sequence 20 nm > 50 nm > 100 nm (nominal size) for both types of surface coatings. Such sequence was consistent with the size distribution in the medium. More than 60% of AgNPs were distributed in the gut of daphnids, indicating that ingestion was the dominant uptake pathway. The size-dependent influx rate was also observed at different AgNPs concentrations. The measured uptake rate constant was lower than that of AgNO(3) at low AgNPs concentration, but it became higher at high AgNPs concentrations. Our study highlighted the indispensability of characterizing the size distribution of AgNPs dispersed in the medium in studying the AgNPs uptake. The accurate quantification of AgNPs influx rate suggested an uptake pathway entirely different from that of AgNO(3) in the daphnids.

Interactions between surfactants and silver nanoparticles of varying charge

The interaction between silver nanoparticles (Ag NPs) of different surface charge and surfactants relevant to the laundry cycle has been investigated to understand changes in speciation, both in and during transport from the washing machine. Ag NPs were synthesized to exhibit either a positive or a negative surface charge in solution conditions relevant for the laundry cycle (pH 10 and pH 7). These particles were characterized in terms of size and surface charge and compared to commercially laser ablated Ag NPs. The surfactants included anionic sodium dodecylbenzenesulfonate (LAS), cationic dodecyltrimethylammoniumchloride (DTAC) and nonionic Berol 266 (Berol). Surfactant–Ag NP interactions were studied by means of dynamic light scattering, Raman spectroscopy, zeta potential, and Quartz Crystal Microbalance. Mixed bilayers of CTAB and LAS were formed through a co-operative adsorption process on positively charged Ag NPs with pre-adsorbed CTAB, resulting in charge reversal from positive to negative zeta potentials. Adsorption of DTAC on negatively charged synthesized Ag NPs and negatively charged commercial Ag NPs resulted in bilayer formation and charge reversal. Weak interactions were observed for nonionic Berol with all Ag NPs via hydrophobic interactions, which resulted in decreased zeta potentials for Berol concentrations above its critical micelle concentration. Differences in particle size were essentially not affected by surfactant adsorption, as the surfactant layer thicknesses did not exceed more than a few nanometers. The surfactant interaction with the Ag NP surface was shown to be reversible, an observation of particular importance for hazard and environmental risk assessments.

Acute and sub-lethal effects in juvenile Atlantic salmon exposed to low μg/L concentrations of Ag nanoparticles

Silver nanoparticles (Ag-NP) are components in numerous commercial products and are discharged into the environment in quantities that are largely unknown. In the present study, juvenile Atlantic salmon were exposed to 1, 20, and 100 μg/L (48 h, static renewal) of a commercially available Ag-NP colloidal suspension in natural (soft) lake water. A solution of AgNO 3 containing 20 μg/L Ag(I) ions was also included to discriminate the effect of NPs from that of ionic silver. Furthermore, the commercial Ag-NP suspension was compared to an in-house synthesised colloidal NP suspension prepared from AgNO 3 and NaBH 4 in citrate buffer. The size distribution of Ag in all exposure solutions was characterised by 0.22 μm filtration and 10 kDa hollow fibre cross-flow ultrafiltration in combination with ICP-MS. All exposures were characterised by a relatively high proportion of Ag-NP in the colloidal size fraction 3–220 nm. For assessment of biological effects, acute toxicity, gill histopathology, blood plasma parameters (Na, Cl, glucose, haemoglobin), and gene expression of a selection of gill biomarkers were measured. Results showed that the gills accumulated Ag in all exposure groups apart from the fish exposed to 1 μg/L Ag-NP. Accumulated Ag caused concentration-dependent response increases in general stress markers such as plasma glucose and gill gene expression of heat shock protein 70. Furthermore, induction of the metallothionein A gene indicated that Ag had been internalized in the gills, whereas a concentration-dependant inhibition of Na/K ATPase expression indicated impaired osmoregulation at as low as 20 μg/L concentrations of Ag-NP. The commercial Ag-NP suspension caused acute gill lamellae necrosis at high concentrations (100 μg/L), potentially giving rise to the substantial (73%) fish mortality at this concentration. The two different Ag-NP preparations gave comparable results for several endpoints measured, but differed in MT-A induction and mortality, thus emphasising the variation in effects that may arise from different Ag-NP preparations.