Abstract  Manufacturers of clothing articles employ nanosilver (n-Ag) as an antimicrobial agent, but the environmental impacts of n-Ag release from commercial products are unknown. The quantity and form of the nanomaterials released from consumer products should be determined to assess the environmental risks of nanotechnology. This paper investigates silver released from commercial clothing (socks) into water, and its fate in wastewater treatment plants (WWTPs). Six types of socks contained up to a maximum of 1360 µg-Ag/g-sock and leached as much as 650 µg of silver in 500 mL of distilled water. Microscopy conducted on sock material and wash water revealed the presence of silver particles from 10 to 500 nm in diameter. Physical separation and ion selective electrode (ISE) analyses suggest that both colloidal and ionic silver leach from the socks. Variable leaching rates among sock types suggests that the sock manufacturing process may control the release of silver. The adsorption of the leached silver to WWTP biomass was used to develop a model which predicts that a typical wastewater treatment facility could treat a high concentration of influent silver. However, the high silver concentration may limit the disposal of the biosolids as agricultural fertilizer.

Abstract  Nanotechnology may yield a plethora of beneficial applications, but it can also be expected to present risks. The challenge is to anticipate and reduce environmental and health risks or, at a minimum, identify and deal with such threats once they begin to become evident. Past experience, particularly with the fuel additive MTBE(methyl tertiary butyl ether), provides valuable guidance on how to assess the potential risks of nanotechnology using a comprehensive environmental assessment approach, which combines a product life-cycle perspective with the risk assessment paradigm. This systematic approach can serve not only to guide the development of a research strategy for assessing the risks of nanotechnology but possibly even help avert unintended consequences of nanotechnology.

Abstract  In this article, we represent a versatile and effective technique which using non-toxic chemicals to prepare stable aqueous dispersions of silver nanoparticles (NPs) via modified Tollens process. It was shown that as-prepared silver colloids consisted of finely-dispersed NPs with average diameter about 10 nm and a relatively narrow size distribution. Moreover, they could be stored very stable after several months without observation of aggregates or sedimentation. In comparison with previous works where Tollens process was being used, we for the first time applied UV-irradiation simultaneously with glucose reduction of silver salt through NPs preparation. The colloidal solutions of silver NPs were found to exhibit a high antibacterial activity against gram-negative Escherichia coli. The concentration of silver leading to a complete inhibition of bacteria growth was revealed as low as at 1.0 μg ml−1 and found much lower compared to earlier reports. These advantages of aqueous dispersions of silver NPs make them ideal for green industrial, medicinal, microbiological and other applications.

Abstract  The magnitude of engineered nanomaterials (ENMs) being produced and potentially released to the environment is a crucial and thus far unknown input to exposure assessment. This work estimates upper and lower bound annual United States production quantities for 5 classes of ENMs. A variety of sources were culled to identify companies producing source ENM products and determine production volumes. Using refining assumptions to attribute production levels from companies with more reliable estimates to companies with little to no data, ranges of U.S. production quantities were projected for each of the 5 ENMs. The quality of data is also analyzed; the percentage of companies for which data were available (via Web sites, patents, or direct communication) or unavailable (and thus extrapolated from other companies' data) is presented.

Abstract  Nanosilver has become one of the most widely used nanomaterials in consumer products because of its antimicrobial properties. Public concern over the potential adverse effects of nanosilver's environmental release has prompted discussion of federal regulation. In this paper, we assess several classes of consumer products for their silver content and potential to release nanosilver into water, air, or soil. Silver was quantified in a shirt, a medical mask and cloth, toothpaste, shampoo, detergent, a towel, a toy teddy bear, and two humidifiers. Silver concentrations ranged from 1.4 to 270,000 microg Ag g product(-1). Products were washed in 500 mL of tap water to assess the potential release of silver into aqueous environmental matrices (wastewater, surface water, saliva, etc.). Silver was released in quantities up to 45 microg Ag g product(-1), and size fractions were both larger and smaller than 100 nm. Scanning electron microscopy confirmed the presence of nanoparticle silver in most products as well as in the wash water samples. Four products were subjected to a toxicity characterization leaching procedure to assess the release of silver in a landfill. The medical cloth released an amount of silver comparable to the toxicity characterization limit. This paper presents methodologies that can be used to quantify and characterize silver and other nanomaterials in consumer products. The quantities of silver in consumer products can in turn be used to estimate real-world human and environmental exposure levels.

Abstract  Since ancient times, people have taken advantage of the antimicrobial effects of colloidal silver particles. Aside from the medical prospects, silver nanoparticles are found in a wide range of commercially available consumer products ranging from cosmetics to household cleansers. Current synthetic methods for creating silver nanoparticles typically call for potentially hazardous chemicals, extreme heat, and produce environmentally dangerous byproducts. Therefore, it is essential that novel

Abstract  Microorganisms have long been known to develop resistance to metal ions either by sequestering metals inside the cell or by effluxing them into the extracellular media. Here we report the biosynthesis of extracellular silver-based single nanocrystallites of well-defined composition and homogeneous morphology utilizing the gamma-proteobacterium, Shewanella oneidensis MR-1, upon incubation with aqueous silver nitrate solution. Further characterization of these particles revealed that the crystals consist of small, reasonably monodispersed spheres in the 2-11 nm size range (average of 4 +/- 1.5 nm). The bactericidal effect of these nanoparticles (biogenic-Ag) is compared to chemically synthesized silver nanoparticles (colloidal-Ag and oleate capped silver nanoparticles, oleate-Ag) and assessed using Gram-negative (E. coli and S. oneidensis) and Gram-positive (B. subtilis) bacteria. Relative toxicity was based on the diameter of inhibition zone in disk diffusion tests, minimum inhibitory concentrations, live/dead assays, and atomic force microscopy. From a toxicity perspective, strain-dependent inhibition depended on the synthesis procedure and the surface coat. Biogenic-Ag was found to be of higher toxicity compared to colloidal-Ag for all three strains tested, whereas E. coli and S. oneidensis were found to be more resistant to either of these nanoparticles than B. subtilis. In contrast, oleate-Ag was not toxic to any of the bacteria. These findings have implications for the potential uses of Ag nanomaterials and for their fate in biological and environmental systems.

Abstract  BACKGROUND: Contaminated surfaces can act as a reservoir for pathogenic microorganisms and potentially exacerbate the risk of infection. Surface disinfection and decontamination provide temporary amelioration against bacterial colonization. Disinfected surfaces eventually become contaminated, thus, mitigating the benefit of the initial disinfection. It is hypothesized that to improve on the current state of the art, a disinfectant should not only immediately disinfect a surface but also provide persistent antimicrobial action after the product has been applied. We describe here a silver-based disinfectant technology designed to provide long-lasting sanitization and disinfection to treated surfaces as evaluated on hard surfaces after repeated environmental insults. METHODS: A comparative evaluation of 6 disinfectant formulations for residual antimicrobial activity after water rinsing was performed. Log reduction of bacterial populations on disinfectant-treated substrates were measured after 30 minutes to 8 hours of exposure and compared with an untreated control. In a similar study, the residual antimicrobial activity of a silver disinfectant was evaluated against antibiotic- and biocide-resistant bacteria also after water rinsing. Further, residual antimicrobial activity of the silver disinfectant was measured after 5 cycles of rinsing, abrasion, and contamination against representative household and nosocomial pathogens (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Enterobacter aerogenes, Enterococcus faecium, or Salmonella choleraesuis) after 10-minute exposure times. RESULTS: In the comparative assay, only the silver disinfectant and a persistent quaternary ammonium compound disinfectant demonstrated significant residual activity (> or =3.0 log(10) reduction to control) against S aureus whereas only the silver disinfectant demonstrated activity against Pseudomonas. No residual activity (< or = 0.5 log reduction to untreated control) was observed for the other disinfectant products. The silver-based disinfectant also showed significant and equivalent efficacy against antibiotic- and silver-resistant bacteria. In addition, the silver disinfectant was able to achieve significant residual activity in 10 minutes against all organisms tested after 1, 3, and 5 cycles of water rinse, abrasion, and microbial contamination. CONCLUSIONS: The findings show the ability of a new silver-based disinfectant to reduce bacterial populations that contact treated surfaces within minutes, highlight the potential to interrupt cross-contamination from environmental surfaces, and reduce the risk of infection within the home and health care settings.

Abstract  The widespread use of silver nanoparticles (Ag-NPs) in commercial products, especially textiles, will likely result in an unknown spread of Ag into the environment. The quantification and characterization of the Ag released from nano-Ag-products is an important parameter needed to predict the effect of Ag-NPs on the environment. The aim of this study was to determine the amount and the form of Ag released during washing from nine fabrics with different ways of silver incorporation into or onto the fibers. The effect of pH, surfactants, and oxidizing agents was evaluated. The results show that little dissolution of Ag-NPs occurs under conditions relevant to washing (pH 10) with dissolved concentrations 10 times lower than at pH 7. However, bleaching agents such as hydrogen peroxide or peracetic acid (formed by the perborate/TAED system) can greatly accelerate the dissolution of Ag. The amount and form of Ag released from the fabrics as ionic and particulate Ag depended on the type of Ag-incorporation into the textile. The percentage of the total silver emitted during one washing of the textiles varied considerably among products (from less than 1 to 45%). In the washing machine the majority of the Ag (at least 50% but mostly >75%) was released in the size fraction >450 nm, indicating the dominant role of mechanical stress. A conventional silver textile did not show any significant difference in the size distribution of the released silver compared to many of the textiles containing nano-Ag. These results have important implications for the risk assessment of Ag-textiles and also for environmental fate studies of nano-Ag, because they show that under conditions relevant to washing, primarily coarse Ag-containing particles are released.

Abstract  Silver ions being less toxic than silver nanoparticles, a more safe material can be obtained to be used as antimicrobial coating. This can be achieved by using thiol chemistry and covalently attach the silver nanoparticles in the coating. Our aim is to produce a coating having antimicrobial properties of silver ions but with the silver nanoparticles firmly attached in the coating. Here, we present a way to produce silver nanoparticles that can be used as a component in a coating or as such to produce an antimicrobial coating. The silver nanoparticles presented here are stabilized by a copolymer (poly(butyl acrylate–methyl methacrylate)) that is soft and has well-known good film-producing properties. The reversible addition-fragmentation chain transfer radical polymerization technique used to prepare the polymers provides conveniently a thiol group for effective binding of the silver nanoparticles to the polymers and thus to the coating.

Abstract  The aim of this study was to use a life-cycle perspective to model the quantities of engineered nanoparticles released into the environment. Three types of nanoparticles were studied: nano silver (nano-Ag), nano TiO2 (nano-TiO2), and carbon nanotubes (CNT). The quantification was based on a substance flow analysis from products to air, soil, and water in Switzerland. The following parameters were used as model inputs: estimated worldwide production volume, allocation of the production volume to product categories, particle release from products, and flow coefficients within the environmental compartments. The predicted environmental concentrations (PEC) were then compared to the predicted no effect concentrations (PNEC) derived from the literature to estimate a possible risk. The expected concentrations of the three nanoparticles in the different environmental compartments vary widely, caused by the different life cycles of the nanoparticle-containing products. The PEC values for nano-TiO2 in water are 0.7 16 µg/L and close to or higher than the PNEC value for nano-TiO2 (<1 µg/L). The risk quotients (PEC/PNEC) for CNT and nano-Ag were much smaller than one, therefore comprising no reason to expect adverse effects from those particles. The results of this study make it possible for the first time to carry out a quantitative risk assessment of nanoparticles in the environment and suggest further detailed studies of nano-TiO2.

Abstract  A one-step chemical reduction route towards silver colloid particles with controllable sizes ranging from 45 to 380 nm is reported in this article. Silver particles, prepared by the reduction of [Ag(NH3)2]+ complex with various reducing sugars, were characterised by means of transmission electron microscopy (TEM), dynamic light scattering (DLS) measurement of particle size distribution, and UV-VIS spectroscopy. The concentration of ammonia in the reaction mixture and the choice of the reducing sugar are the key parameters in the control of particle size. Synthesised silver colloid particles were successfully tested for use in surface-enhanced Raman spectroscopy (SERS) with 1-methyladenine as a testing substance.

Abstract  This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10–500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size <100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.

Abstract  Silver is a naturally occurring metal that is extensively utilized in the photographic and imaging industry, as well as in electronics and electrical alications and other lesser uses. It is known to be discharged to the environment from its industrial applications, and this leads to the possibility for exposure to aquatic and terrestrial organisms. Because of great differences in toxicity between silver compounds, the form in which silver enters the environment is important. While the ionic form of silver has been shown to be toxic to a variety of aquatic organisms, forms of silver other than ionic, or free, silver are significantly less toxic. Ionic silver is known to convert to the more innocuous forms as it reacts rapidly with natural chemical ligands in sewer systems, sewage treatment facilities, and the environment. This paper reviews information on the industries that use silver, the quantities they employ, and the forms and amounts of silver that may be discharged from each into the environment.

Abstract  This paper describes a simple and convenient procedure based on the Tollens process for the preparation of silver nanoparticles with a relatively narrow distribution in size. The starting reagents were similar to those commonly used in the electroless deposition of silver. Only under appropriate conditions, mixing of these reagents was able to generate stable aqueous dispersions of silver colloids rather than thin films of silver deposited on the surfaces of objects immersed in the plating solution (including the interior surface of the container). We have demonstrated the capability and feasibility of this approach by forming silver nanoparticles with dimensions in the range of 20–50 nm. These silver nanoparticles could exist as very stable dispersions in water, or as submonolayer coating on microscale colloids. We have also explored the use of light scattering simulation to study the oxidation (by air) of these nanoparticles.

Abstract  Noble metallic nanomaterials are of particular interest today because of their applications in many areas. The selected topic is one of the most active regions in the metallic nanomaterials. First, common synthetic methods of silver nanomaterials, e.g., chemical reduction, photochemical method, ultrasonic-assisted reduction, electrochemical method, template, irradiating reduction and biochemical method, are introduced. The advantages and drawbacks of these methods are also reviewed. Secondly, we mainly discuss the formation of silver nanoparticles in microemulsion. Besides an introduction to the concept, type and formation of microemulsion, we focus especially on the influencing factors of silver nanoparticle formation. Effects of the type of continuous phase, molar ratio of water to surfactant (W), precursor concentration and reductant type and concentration on the particle formation are summarized and evaluated. Furthermore, current and possible developing trends of the synthetic technology of silver nanoparticles are also prospected.

Abstract  An apparatus and method for producing colloidal silver. A large-volume container, such as a fifteen gallon container, includes a hinged lid on which a rotational impeller is mounted along with several sets of electrodes that are electrically connected to a power transformer. The container is partially filled with water, and when the lid is closed, the sets of electrodes are disposed in communication with the water in a predetermined arrangement, and the impeller resides submerged in the water. Certain of the electrodes constitute silver wire. The power transformers convey current to the electrodes, preferably alternating current, at voltages sufficient to cause silver particles to separate from the silver wire and enter the solution in a stable, suspended state. The impeller is rotated, preferably continuously, to prevent the suspended silver from remaining in upper levels of the water, thereby dispersing the silver particles more uniformly throughout the volume of water.

Abstract  The present invention relates to the preparation of nanoparticles of silver (Ag) and silver alloyed with other elements such as platinum (Pt), gold (Au), aluminum (Al), cadmium (Cd), and sulfur (S) in surfactant solutions. The surfactant molecules have the intrinsic property to absorb into the interface, which are formed between two different phases. Thus, the surfactant molecules would adsorb into the surface of nuclei in solution. The adsorbed surfactant molecules from the solution prevent the coalescence of particles and control the rate of particle growth. By choosing the proper kind and/or concentration of surfactants, the size of particles formed in solution can be controlled in nm scale.

Abstract  Bio-inspired silver nanoparticles were synthesized with the aid of a novel, non-toxic, eco-friendly biological material namely, banana peel extract (BPE). Boiled, crushed, acetone precipitated, air-dried peel powder was used for reducing silver nitrate. Silver nanoparticles were formed when the reaction conditions were altered with respect to pH, BPE content, concentration of silver nitrate and incubation temperature. The colorless reaction mixtures turned brown and displayed UV–visible spectra characteristic of silver nanoparticles. Scanning electron microscope (SEM) observations revealed the predominance of silver nanosized crystallites after short incubation periods. When the reaction mixtures were incubated for 15 days, some micro-aggregates were also observed. Energy dispersive spectrometer (EDS) studies and X-ray diffraction analysis confirmed the presence of silver nanoparticles. Fourier transform infra-red spectroscopy (FTIR) indicated the role of different functional groups (carboxyl, amine and hydroxyl) in the synthetic process. These silver nanoparticles displayed antimicrobial activity against fungal as well as bacterial cultures.