The Application of 2,6-Bis(4-Methoxybenzoyl)-Diaminopyridine in Solvent Extraction and Polymer Membrane Separation for the Recovery of Au(III), Ag(I), Pd(II) and Pt(II) Ions from Aqueous Solutions.

The work describes the results of the first application of 2,6-bis(4-methoxybenzoyl)-diaminopyridine (L) for the recovery of noble metal ions (Au(III), Ag(I), Pd(II), Pt(II)) from aqueous solutions using two different separation processes: dynamic (classic solvent extraction) and static (polymer membranes). The stability constants of the complexes formed by the L with noble metal ions were determined using the spectrophotometry method. The results of the performed experiments clearly show that 2,6-bis(4-methoxybenzoyl)-diaminopyridine is an excellent extractant, as the recovery was over 99% for all studied noble metal ions. The efficiency of 2,6-bis(4-methoxybenzoyl)-diaminopyridine as a carrier in polymer membranes after 24 h of sorption was lower; the percentage of metal ions removal from the solutions (%Rs) decreased in following order: Ag(I) (94.89%) > Au(III) (63.46%) > Pt(II) (38.99%) > Pd(II) (23.82%). The results of the desorption processes carried out showed that the highest percentage of recovery was observed for gold and silver ions (over 96%) after 48 h. The results presented in this study indicate the potential practical applicability of 2,6-bis(4-methoxybenzoyl)-diaminopyridine in the solvent extraction and polymer membrane separation of noble metal ions from aqueous solutions (e.g., obtained as a result of WEEE leaching or industrial wastewater).

Preparation and antioxidant study of silver nanoparticles of Microsorum pteropus methanol extract.

This study reports a preparation of silver nanoparticles (SNPs) using Microsorum pteropus methanol extract, as a new approach in the development of therapeutic strategies against diseases caused by oxidative stress, reactive oxygen, and nitrogen species. During the effort of extraction and isolation from M. pteropus, X-ray single-crystal structural analysis of sucrose was succeeded. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide scavenging assay were used to confirm the antioxidant potential. Preparation of SNPs was confirmed by ultraviolet-visible (UV-Vis) spectra with peaks between 431 and 436 nm. Infrared (IR) analysis showed OH, NH functional groups of alcohol, phenol, amine, and aliphatic CH stretching vibrations of hydrocarbon chains of the synthesized nanoparticles. The antioxidant properties of the SNPs significantly showed DPPH reduction with an IC50 value of 47.0 µg/mL and hydrogen peroxide scavenging activity with an IC50 value of 35.8 µg/mL, and hence, indicating their capability to eliminate potentially damaging oxidants involved in oxidative stress and their related diseases.

Datura suaveolens and Verbena tenuisecta mediated silver nanoparticles, their photodynamic cytotoxic and antimicrobial evaluation.

Biogenic production of nanoparticles is eco-friendly, less expensive method with various medical and biological applications. Nanotechnology along with photodynamic therapy is gaining tremendous importance with enhanced efficacy. The present work was aimed to evaluate methanolic extracts and nanoparticles of two selected plants (Datura suavolens and Verbina tenuisecta) for cytotoxic photodynamic, antioxidant and antimicrobial study. Both extract and silver (5 mM) nanoparticles of Datura plant showed significant activities against bacterial strains. Maximum ZOI of 27.3 ± 1.6 mm was observed with nanoparticles of Datura branches with minimum inhibitory (MIC) value of 32 µg/ml. In case of antifungal and antioxidant assay samples were moderately active. Silver nanoparticles and extracts were effective against rhabdomyosarcoma cell line with lowest IC50 value of 42.5 ± 0.6 µg/ml and percent viability of 25.6 ± 1.3 of Verbena tenuisecta. However, nanoparticles of Datura leaves and branches were more potent with IC50 value of 2.4 ± 0.9 µg/ml and 7.8 ± 1.1 µg/ml respectively. The result of photodynamic study showed that efficacy of photosensitizer was enhanced and percent viability reduced when nanoparticles used as an adjunct. The color change and UV spectra (415‒425 nm) indicated the production of nanoparticles. Fourier transform infrared spectroscopy (FTIR) spectra showed presence of different functional groups e.g., hydroxyl, carbonyl and amino. Nanoparticles are sphenoid in morphology and size ranges between 20-150 nm. Current study showed these silver nanoparticles can be used as cytotoxic agent in photodynamic therapy and can play a critical role to establish medicinal potential of selected plants.

Antioxidant, antimicrobial and cytotoxic potential of silver nanoparticles synthesized using flavonoid rich alcoholic leaves extract of Reinwardtia indica.

The present work discusses the establishment of a green route for the rapid synthesis of silver nanoparticles (AgNPs) using an alcoholic extract of Reinwardtia indica (AERI) leaves which act as a reducing as well as a capping agent. The change in color from yellowish green to dark brown confirmed the synthesis of AgNPs. A characteristic surface plasmon resonance (SPR) band at 436 nm advocated the presence of AgNPs. The synthesis process was optimized using one factor at a time approach where 1.0 mM AgNO3 concentration, 5 mL 0.4% (v/v) of AER inoculum dose and 30 min of sunlight exposure were found to be the optimum conditions. The synthesized AgNPs was characterized by several characterizing techniques such as HR- TEM, SAED, HR-SEM, EDX, XRD, FTIR and AFM analysis. For evaluation and comparison of AgNPs with AERI used human pathogen E. coli, P. aeurogenosa, S. aeurus and C. albicans for antimicrobial, for cytotoxicity study SiHa cell line at concentration of (10, 50, 100, 250 and 500 µg mL-1) and for enzymatic assay superoxide dismutase, catalase, malondialdehyde and glutathione peroxidase method were used. The size of nanoparticle in the range of 3-15 nm was confirmed TEM, spherical shape by SEM and crystal lattice nature by XRD. AFM results revealed the 2 D and 3 D pattern of particle scatter nature on the surface. This protocol as simple, rapid, one step, eco-friendly, nontoxic and AgNPs showed strong antimicrobial activity as well as cytotoxic potential in comparison to AERI.

Extracellular biosynthesis, characterization, optimization of silver nanoparticles (AgNPs) using Bacillus mojavensis BTCB15 and its antimicrobial activity against multidrug resistant pathogens.

Biosynthesis of metal nanoparticles is an area of interest among researchers because of its eco-friendly approach. Current study focuses at biosynthesis of silver nanoparticles (AgNPs) and optimization of physico-chemical conditions to obtain mono-dispersed and stable AgNPs having antimicrobial activity. Initially Bacillus mojavensis BTCB15 produced silver nanoparticles (AgNPs) of 105 nm. Silver nanoparticles (AgNPs) were characterized by particle size analyzer, UV-Vis Spectroscopy, Fourier transforms infrared spectroscopy (FTIR), Atomic force microscopy (AFM), and X-ray diffraction (XRD). Whereas, under optimal conditions of temperature 55 °C, pH 8, addition of surfactant Tween 20, and metal ion K2SO4, about 104% size reduction was achieved with average size of 2.3nm. Molecular characterization revealed 98% sequence homology with Bacillus mojavensis. AgNPs exhibited antibacterial activity at concentrations ranging from 0.5 to 2.5 µg/µl against Escherichia coli BTCB03, Klebsiella pneumonia BTCB04, Acinetobacter sp. BTCB05, and Pseudomonas aeruginosa BTCB01 but none against Staphylococcus aureus BTCB02. Highest antibacterial activity was observed at 0.27 µg/µl and lowest at 0.05 µg/µl of AgNPs indicated by zone of inhibition. Conclusively, under optimum conditions, Bacillus mojavensis BTCB15 was able to produce AgNPs of 2.3 nm size and had antibacterial activity against multi drug resistant pathogens.

Selective separation of Cu, Ni and Ag from printed circuit board waste using an environmentally safe technique.

Printed circuit boards (PCBs) make up a large part of e-waste and include high concentrations of high-value metals. Therefore, the recovery of these metals is interesting from both the environmental and economic points of view. Here, the extraction/separation of copper, nickel and silver from PCB leachate was studied using an aqueous two-phase system (ATPS) formed by triblock copolymers with an electrolyte and water, which is in compliance with the principles of green chemistry. The best conditions for the selective extraction consisted of 1-(2-pyridylazo)-2-naphthol (3.5 mmol kg-1) at pH = 6.0 in 6 sequential steps for the Cu(II), dimethylglyoxime (5.00 mmol kg-1) at pH = 9.0 for the Ni(II) and thiocyanate (5.20 mmol kg-1) at pH = 9.0 for the Ag(I). These conditions were applied sequentially for extraction of Cu, Ni and Ag from the PCB leachate, obtaining high separation factor (S) values between the analyte and the metallic concomitants (SCu,Ni = 1,460, SCu,Fe = 15,500, SCu,Ag = 15,900, SNi,Fe = 32,700, SNi,Ag = 34,700 and SAg,Fe = 4800). The maximum extraction percentages (%E) for Cu, Ni and Ag were 99.9%, 99.9% and 99.8%, respectively. After the extraction, a single step stripping process was performed, resulting in more than 82% of the ion available in a clean lower phase. For the first time, an ATPS has been used for sequential extraction of several metal analytes from a real sample.

Green synthesis and characterization of silver nano-particles from pharmaceutically important Periploca hydaspidis and their biological activity.

The present study describes the synthesis, characterization of nano-particles from Periploca hyaspidis and their in vitro biological activity. The synthesis of AgNPs was confirmed by UV-Vis spectrophotometer and structure by atomic force microscope. The crystallite size and different functional groups was determined by X-ray diffraction and Fourier transformed infrared spectroscopy. Anti-microbial and anti-oxidant activity was carried out by disc diffusion and DPPH radical scavenging protocol respectively. Silver nano-particles (AgNPs) were synthesized by mixing 1mM AgNO3 solutions with plant boiled extract in 1:9. The color change from yellow to dark brown indicated the synthesis of the nano-particles. The AgNPs were more stable at 25°C to 45°C, 1mM concentration of the salt and neutral to slightly basic pH. The results revealed that aromatic amines were responsible for the synthesis of AgNPs. The crystallite size was 7.50 nm, cubic and in nanorgime. AgNPs showed good anti-oxidant activity and was effective against K. pnemoniae, E. coli, X. compestris, C. albicans and P. chrysogenum.

Evaluation of anthelmintic activity of biologically synthesized silver nanoparticles against the gastrointestinal nematode, Haemonchus contortus.

The present study focuses on the in vitro anthelmintic activity of silver nanoparticles (AgNPs) synthesized using the aqueous extract of Azadirachta indica against Haemonchus contortus. The synthesized AgNPs were characterized by ultraviolet-visible (UV-Vis) spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies. The UV-Vis spectrum exhibited a sharp peak at 420 nm, which was validated by electron microscopy, indicating the preparation of spherical nanoparticles measuring 15-25 nm in size. The in vitro study was based on an egg hatch assay (EHA) and adult motility inhibition assays. Six concentrations of AgNPs were used for EHA, ranging from 0.00001 to 1.0 µg/ml, and a range of 1-25 µg/ml was used for adult worms. The highest concentration induced 85 ± 2.89% egg hatch inhibition. The IC50 value for EHA was 0.001 µg/ml, whereas in vitro adult H. contortus motility inhibition was produced at 7.89 µg/ml (LC50). The effectiveness of A. indica leaf extract (aqueous) was also evaluated, which showed an IC50 value for EHA of 115.67 µg/ml, while the LC50 against adult H. contortus was 588.54 µg/ml. The overall findings of the present study show that the experimental plant extract contains reducing properties for the synthesis of AgNPs which, in turn, showed potent anthelmintic properties. This is the first report where AgNPs have been tested for their anthelmintic properties in an in vitro model.

Electrophoretic Separation of Single Particles Using Nanoscale Thermoplastic Columns.

Phenomena associated with microscale electrophoresis separations cannot, in many cases, be applied to the nanoscale. Thus, understanding the electrophoretic characteristics associated with the nanoscale will help formulate relevant strategies that can optimize the performance of separations carried out on columns with at least one dimension below 150 nm. Electric double layer (EDL) overlap, diffusion, and adsorption/desorption properties and/or dielectrophoretic effects giving rise to stick/slip motion are some of the processes that can play a role in determining the efficiency of nanoscale electrophoretic separations. We investigated the performance characteristics of electrophoretic separations carried out in nanoslits fabricated in poly(methyl methacrylate), PMMA, devices. Silver nanoparticles (AgNPs) were used as the model system with tracking of their transport via dark field microscopy and localized surface plasmon resonance. AgNPs capped with citrate groups and the negatively charged PMMA walls (induced by O2 plasma modification of the nanoslit walls) enabled separations that were not apparent when these particles were electrophoresed in microscale columns. The separation of AgNPs based on their size without the need for buffer additives using PMMA nanoslit devices is demonstrated herein. Operational parameters such as the electric field strength, nanoslit dimensions, and buffer composition were evaluated as to their effects on the electrophoretic performance, both in terms of efficiency (plate numbers) and resolution. Electrophoretic separations performed at high electric field strengths (>200 V/cm) resulted in higher plate numbers compared to lower fields due to the absence of stick/slip motion at the higher electric field strengths. Indeed, 60 nm AgNPs could be separated from 100 nm particles in free solution using nanoscale electrophoresis with 100 µm long columns.

Toward full spectrum speciation of silver nanoparticles and ionic silver by on-line coupling of hollow fiber flow field-flow fractionation and minicolumn concentration with multiple detectors.

The intertransformation of silver nanoparticles (AgNPs) and ionic silver (Ag(I)) in the environment determines their transport, uptake, and toxicity, demanding methods to simultaneously separate and quantify AgNPs and Ag(I). For the first time, hollow fiber flow field-flow fractionation (HF5) and minicolumn concentration were on-line coupled together with multiple detectors (including UV-vis spectrometry, dynamic light scattering, and inductively coupled plasma mass spectrometry) for full spectrum separation, characterization, and quantification of various Ag(I) species (i.e., free Ag(I), weak and strong Ag(I) complexes) and differently sized AgNPs. While HF5 was employed for filtration and fractionation of AgNPs (>2 nm), the minicolumn packed with Amberlite IR120 resin functioned to trap free Ag(I) or weak Ag(I) complexes coming from the radial flow of HF5 together with the strong Ag(I) complexes and tiny AgNPs (<2 nm), which were further discriminated in a second run of focusing by oxidizing >90% of tiny AgNPs to free Ag(I) and trapped in the minicolumn. The excellent performance was verified by the good agreement of the characterization results of AgNPs determined by this method with that by transmission electron microscopy, and the satisfactory recoveries (70.7-108%) for seven Ag species, including Ag(I), the adduct of Ag(I) and cysteine, and five AgNPs with nominal diameters of 1.4 nm, 10 nm, 20 nm, 40 nm, and 60 nm in surface water samples.

Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli.

Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV-visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 10(8) particles/ml with mode particles sizes of approx. 90-100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5×10(5) and 10(7) particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively.

Simultaneous mass quantification of nanoparticles of different composition in a mixture by microdroplet generator-ICPTOFMS.

This work investigated the potential of a high temporal resolution inductively coupled plasma time-of-flight mass spectrometer (ICPTOFMS) in combination with a microdroplet generator (MDG) for simultaneous mass quantification of different nanoparticles (NPs) in a mixture. For this purpose, a test system containing certified Au NPs, well characterized Ag NPs, and core-shell NPs composed of an Au core and an Ag shell was employed. Thanks to the full spectra coverage and rapid simultaneous detection of the TOFMS, the element composition of individual particles can be determined. The pure Ag NPs and the core-shell NPs could be differentiated despite the same mass of Ag they contain. Calibration with monodisperse droplets consisting of standard solutions allowed for the mass quantification of NPs without the use of NP certified materials. On the basis of this mass quantification, the sizes of NPs originating from the same aqueous suspension were simultaneously determined with an accuracy of 7-12%. The size-equivalent limits of detection estimated with the 3*σ criterion were 13 nm for Au and 16 nm for Ag. Estimation of the LODs using Poisson statistics resulted in 19 and 27 nm, respectively. In addition, the 30 µs temporal resolution of the ICPTOFMS allowed studying interactions of NPs with the ICP based on their transient MS signals. The results demonstrated a difference in vaporization behavior of the core-shell NPs and solutions and indicated that vaporization of the Ag shell takes place prior to the Au core.

Atmospheric Hg emissions from preindustrial gold and silver extraction in the Americas: a reevaluation from lake-sediment archives.

Human activities over the last several centuries have transferred vast quantities of mercury (Hg) from deep geologic stores to actively cycling earth-surface reservoirs, increasing atmospheric Hg deposition worldwide. Understanding the magnitude and fate of these releases is critical to predicting how rates of atmospheric Hg deposition will respond to future emission reductions. The most recently compiled global inventories of integrated (all-time) anthropogenic Hg releases are dominated by atmospheric emissions from preindustrial gold/silver mining in the Americas. However, the geophysical evidence for such large early emissions is equivocal, because most reconstructions of past Hg-deposition have been based on lake-sediment records that cover only the industrial period (1850-present). Here we evaluate historical changes in atmospheric Hg deposition over the last millennium from a suite of lake-sediment cores collected from remote regions of the globe. Along with recent measurements of Hg in the deep ocean, these archives indicate that atmospheric Hg emissions from early mining were modest as compared to more recent industrial-era emissions. Although large quantities of Hg were used to extract New World gold and silver beginning in the 16th century, a reevaluation of historical metallurgical methods indicates that most of the Hg employed was not volatilized, but rather was immobilized in mining waste.

Rapid chromatographic separation of dissoluble Ag(I) and silver-containing nanoparticles of 1-100 nanometer in antibacterial products and environmental waters.

Sensitive and rapid methods for speciation analysis of nanoparticulate Ag (NAg) and Ag(I) in complex matrices are urgently needed for understanding the environmental effects and biological toxicity of silver nanoparticles (AgNPs). Herein we report the development of a universal liquid chromatography (LC) method for rapid and high resolution separation of dissoluble Ag(I) from nanoparticles covering the entire range of 1-100 nm in 5 min. By using a 500 Å poresize amino column, and an aqueous mobile phase containing 0.1% (v/v) FL-70 (a surfactant) and 2 mM Na2S2O3 at a flow rate of 0.7 mL/min, all the nanoparticles of various species such as Ag and Ag2S were eluted in one fraction, while dissoluble Ag(I) was eluted as a baseline separated peak. The dissoluble Ag(I) was quantified by the online coupled ICP-MS with a detection limit of 0.019 µg/L. The NAg was quantified by subtracting the dissoluble Ag(I) from the total Ag content, which was determined by ICP-MS after digestion of the sample without LC separation. While the addition of FL-70 and Na2S2O3 into the mobile phase is essential to elute NAg and Ag(I) from the column, the use of 500 Å poresize column is the key to baseline separation of Ag(I) from ∼ 1 nm AgNPs. The feasibility of the proposed method was demonstrated in speciation analysis of dissoluble Ag(I) and NAg in antibacterial products and environmental waters, with very good chromatographic repeatability (relative standard deviations) in both peak area (<2%) and retention time (<0.6%), excellent spiked recoveries in the range of 84.7-102.7% for Ag(I) and 81.3-106.3% for NAg. Our work offers a novel approach to rapid and baseline separation of dissoluble metal ions from their nanoparticulate counterparts covering the whole range of 1-100 nm.

Biosynthesis of silver nanoparticles.

Metal nanoparticles have unique optical, electronic, and catalytic properties. There exist well-defined physical and chemical processes for their preparation. Those processes often yield small quantities of nanoparticles having undesired morphology, and involve high temperatures for the reaction and the use of hazardous chemicals. Relatively, the older technique of bioremediation of metals uses either microorganisms or their components for the production of nanoparticles. The nanoparticles obtained from bacteria, fungi, algae, plants and their components, etc. appear environment-friendly, as toxic chemicals are not used in the processes. In addition to this, the formation of nanoparticles takes place at almost normal temperature and pressure. Control of the shape and size of the nanoparticles is possible by appropriate selection of the pH and temperature. Three important steps are the bioconversion of Ag+ ions, conversion of desired crystals to nanoparticles, and nanoparticle stability. Generally, nanoparticles are characterized by the UV-visible spectroscopy and use of the electron microscope. Silver nanoparticles are used as antimicrobial agents and they possess antifungal, anti-inflammatory, and anti-angiogenic properties. This review highlights the biosynthesis of silver nanoparticles by various organisms, possible mechanisms of their synthesis, their characterization, and applications of silver nanoparticles.

Synthesis of gold and silver nanoparticles using leaf extract of Perilla frutescens--a biogenic approach.

The present investigation demonstrates a rapid biogenic approach for the synthesis of gold and silver nanoparticles using biologically active and medicinal important Perilla frutescens leaf extract as a reducing and stabilizing agent under ambient conditions. Gold and silver nanoparticles were first synthesized from Perilla frutescens leaf extract which was used as a vegetable and in traditional medicines for a long time in Korea, Japan, and China. The nanoparticles obtained were characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Surface plasmon resonance spectra of gold and silver nanoparticles were obtained at 540 and 430 nm and triangular and spherical shape respectively. TEM studies showed that the particle sizes of gold and silver nanoparticles ranges -50 nm and -40 nm respectively. X-ray diffraction studies confirm that the biosynthesized nanoparticles were crystalline gold and silver. Fourier transform infra-red spectroscopy revealed that biomolecules were involved in the synthesis and capping of the nanoparticles produced. XRD and EDX confirmed the formation of gold and silver nanoparticles. This is a simple, efficient and rapid method to synthesize gold and silver nanoparticles at room temperature without use of toxic chemicals. Obtained gold and silver nanoparticles can be used in various biomedical and biotechnological applications.

Efficient proteolysis and application of an alkaline protease from halophilic Bacillus sp. EMB9.

A salt-stable alkaline protease from moderately halophilic Bacillus sp. EMB9, isolated from the western coast of India, is described. This protease was capable of efficiently removing silver from used/waste X-Ray films, as well as hydrolyzing defatted soy flour with 31% degree of hydrolysis (DH). Production of the protease was optimized by using response surface methodology. Ca(2+) and NaCl were the most critical factors in enhancing the yield. Under optimized culture conditions, a maximum of 369 U protease/mL was obtained, which is quite comparable to the yields of commercial proteases. The elevated production level coupled with ability to efficiently hydrolyze protein-laden soy flour and complete recovery of silver from used X-Ray films makes it a prospective industrial enzyme.

Supramolecular solvent-based extraction coupled with vortex-mixing for determination of palladium and silver in water samples by flame atomic absorption spectrometry.

A simple and practical extraction method of supramolecular solvents (SUPRAS) was developed for separation and enrichment of trace amounts of palladium (Pd) and silver (Ag) in water samples prior to flame atomic absorption spectrometry (FAAS) analysis. The SUPRAS selected was made up of an aqueous solution containing tetrahydrofuran and nonanoic acid. Pd and Ag reacted with diethyldithiocarbamate to form hydrophobic chelates, which were extracted into the vesicles of SUPRAS. Different parameters such as the concentration of chelating agent, sample pH, supramolecular solvent and the effect of foreign ions were studied. Under the optimal conditions, the linear ranges of Pd and Ag were from 10 to 1,000 µg/L. The relative recoveries of Pd and Ag in tap and river water samples at the spiking level of 10 ug/mL ranged from 90.8 to 116%. The relative standard deviations were 3.6-4.0% (n = 9), the limits of detection were 2.8 and 1.9 µg/L and the enrichment factors were 36 and 18 for Pd and Ag, respectively. The quantification limits were 3.2 and 2.4 µg/L. The method was successfully applied to the determination of Pd and Ag in water samples.

[Bioaccumulation of silver and gold nanoparticles in organs and tissues of rats by neutron activation analysis].

Bioaccumulation of silver (Ag) and gold (Au) nanoparticles (NPs) with mean sizes of 6 nm and 35 nm, respectively, has been studied after their intragastric administration to rats at a dose of 100 µg/kg of body weight for 28 or 14 days. The organs and tissues (liver, kidney, spleen, heart, gonads brain, and blood) were subjected to thermal neutron activation, and, then, the activity of the 110mAg and 198Au isotopes generated was measured. The NPs of both metals were detected in all biological samples studied, the highest specific weight and content of Ag NP being found in the liver, and those of Au being found in kidneys of animals. The content of Ag NPs detected in the brain was 66.4 ± 5.6 ng (36 ng/g tissue), no more than 7% ofthese NPs being localized in the lumen of brain blood vessels. The content of Ag and Au NPs found in organs and tissues of rats could be regarded as nonhazardous (nontoxic) in accordance with the known literature data.

'Sticky electrodes' for the detection of silver nanoparticles.

Detection and quantification of nanoparticles in environmental systems is a task that requires reliable and affordable analytical methods. Here an approach using a cysteine-modified 'sticky' glassy carbon electrode is presented. The electrode is immersed in a silver nanoparticle containing electrolyte and left in this suspension without an applied potential, i.e. under open circuit condition, for a variable amount of time. The amount of silver nanoparticles immobilized on the electrode within this sticking time is then determined by oxidative stripping, yielding the anodic charge and thus the amount of Ag nanoparticles sticking to the electrode surface. When using a cysteine-modified glassy carbon electrode, significant and reproducible amounts of silver nanoparticles stick to the surface, which is not the case for unmodified glassy carbon surfaces. Additionally, proof-of-concept experiments are performed on real seawater samples. These demonstrate that also under simulated environmental conditions an increased immobilization and hence improved detection of silver nanoparticles on cysteine-modified glassy carbon electrodes is achieved, while no inhibitive interference with this complex matrix is observed.