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Straight silver nanowires were synthesized by accelerated oxidization and then aligned into ordered arrays by off-center spin-coating. Seesaw-like behavior was observed in the polarized transmission spectra of the arrays. With the increment of polarization angle (θP, defined as the angle between axis of nanowires and direction of electric field of light), transmission changed repeatedly with a period of 180°, but it moved to opposite directions between the two regions separated by supporting points locating at 494 nm. The behavior is ascribed to the competition between the extinction behaviors of the two modes of surface plasma polaritons on silver nanowires. One is the longitudinal mode which is excited by long wavelengths and tuned by function of cos2( θ p ) and the other is the transverse mode that is excited by short wavelengths and tuned by function of sin2( θ p ). Simulation was performed based on the finite-difference time domain method. The effect of the nanowire diameter and length (aspect ratio) on the position of the supporting point was studied. As nanowire width increased from 20 nm to 350 nm, the supporting point moved from 400 to 500 nm. While it changed slightly when the nanowire length increased from 3 μm to infinitely long (width fixed at 260 nm). In current study, the position of the supporting point is mainly determined by the nanowire width. [ABSTRACT FROM AUTHOR]

Photochromic transitions in silver nanoparticles (AgNPs) embedded titanium dioxide (TiO2) films under green light illumination are marked by reduction in strength and blue shift in the position of the localized surface plasmon resonance (LSPR) associated with AgNPs. These transitions, which happen in the sub-nanometer length scale, have been analysed using the variations observed in the effective dielectric properties of the Ag-TiO2 nanocomposite films in response to the size reduction of AgNPs and subsequent changes in the surrounding medium due to photo-oxidation. Bergman- Milton formulation based on spectral density approach is used to extract dielectric properties and information about the geometrical distribution of the effective medium. Combined with finite element method simulations, we isolate the effects due to the change in average size of the nanoparticles and those due to the change in the dielectric function of the surrounding medium. By analysing the dynamics of photochromic transitions in the effective medium, we conclude that the observed blue shift in LSPR is mainly because of the change in the dielectric function of surrounding medium, while a shape-preserving effective size reduction of the AgNPs causes decrease in the strength of LSPR. [ABSTRACT FROM AUTHOR]

We report on the shallow synthesis by low energy ion implantation of delta-layers of Ag nanocrystals in SiO2 at few nanometers under its free surface. Transmission electron microscopy observations, ballistic simulations, and reflectance measurements are coupled to define the conditions for which the synthesis is fully controlled and when, on the contrary, this control is lost. We show that low dose implantation leads to the formation of a well-defined single plane of nanocrystals, while for larger doses, sputtering and diffusion effects limit the control of the size, position, and volume amount of these nanocrystals. This paper provides the experimental evidence of the incorporated dose saturation predicted in the literature when implanting metal ions at high doses in glass matrices. Its consequences on the particle population and the plasmonic optical response of the composite layers are carefully analyzed. We show here that this saturation phenomenon is underestimated in standard simulation predictions due to diffusion of metal atoms towards the surface and nanocrystal nucleation during the implantation process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A silver iron core-shell nanostructure was synthesised in a facile and green manner. • C. sempervirens aqueous extract was used for reduction of both Ag+ and Fe3+ ions. • The prepared nanostructures showed both antimicrobial and catalytic activity. • Iron coating increases the antimicrobial properties of AgNPs. Abstract Bringing two completely different properties into one nanostructure by using individual metals is a difficult goal to achieve. However, recently core-shell metallic nanostructures have introduced as a novel multifunctional nanomaterial with enhanced properties. Iron and silver based nanoparticles are among the most widely applicable nanomaterials in modern industries. Zero-valent iron nanostructures and silver nanoparticles are well known for their applications as catalyst and antimicrobial agent, respectively. In the present study, for the first time, we are reporting a successful fabrication of zero valent iron coated silver nanoparticles (ZVI@AgNPs) by using a green and one-pot synthesis approach. Aqueous leaf extract of Mediterranean cypress (Cupressus sempervirens) was used as a natural source of reducing and capping agent for reduction of both Ag+ and Fe3+ ions. Prepared nanostructures were characterised by a range of analytical techniques namely UV–vis spectroscopy, Transmission Electron Microscopy, X-Ray Diffraction, and Fourier Transform Infra-Red Spectroscopy. The prepared nanostructures were found to be an effective material for dye removal and were capable to remove 98.5% of the initial dye just after 4 h. Based on the results, zero valent iron coating enhanced the antimicrobial potential of AgNPs against Gram-positive bacteria (S. aureus), while showing no significant enhancement against Gram-negative bacteria (E. coli). ZVI@AgNPs, therefore, can be introduced as a novel nanostructure for application in aquatic filter materials to simultaneously reduce microbial and organic contaminants. [ABSTRACT FROM AUTHOR]

The development of cost-effective simple methods to fabricate nanocomposites based on metal oxide (MOX) supported noble metals with improved performance is extremely demanding, specifically in the field of nanomaterial and gas sensor. In this this work, a facile one-step hydrothermal strategy to synthesize strongly-coupled TiO2 nanosheets supported with Ag nanoparticles (Ag/TiO2 heterojunction nanocomposites) is proposed, which is proved of high effectiveness for sensor applications. The structure and morphology of synthesized nanocomposites was performed by XRD, XPS, HRTEM, UV-Vis and PL spectroscopy. Compared to pristine TiO2, the sensors based on such Ag/TiO2 heterojunction nanocomposites show excellent ethanol gas sensing properties in terms of high sensitivity (8.5 towards 100 ppm), selectivity against other gases (methanal, acetone, and methanol), short response/recover times (9/10 s), and high stability (present stable response after 30 days). Such performance demonstrates this material is promising for practical gas sensor applications. [ABSTRACT FROM AUTHOR]

The functionalization of nanoparticles (NPs) by utilizing biologically important substances through a green route is a novel aspect of the design of a colorimetric sensor. In this work, we use the bifunctional Jamun ( Syzygium cumini ) stabilized silver nanoparticles (J–AgNPs) for simultaneous colorimetric detection of Al(III) and the disinfection of synthetic and real contaminated groundwater samples. The J–AgNPs were prepared under natural sunlight irradiation by utilizing Jamun leaves extract (JLE) as both the reducing agent and the stabilizer. The lower detection limit for Al(III) with this method is 0.01 ppm (S/N = 3), which falls within the permissible limits set by the Environmental Protection Agency (USEPA), that is, 50 ppm. The proposed method also displays the excellent antibacterial activity with the value of 45 μg/mL (IC 50 ) for S. aureus bacteria and 25 μg/mL (IC 50 ) for E. coli bacteria. The estimated total cost of the prepared nanosensor (100 mL) is US $ 0.03, which makes the present method cost-effective in areas with resource-limited settings. As far as we know, this is the first study to use natural sunlight as a source of energy for the generation of J–AgNPs in an aqueous medium, making the process environmentally friendly, attractive and efficient. [ABSTRACT FROM AUTHOR]

In this study, silver nanoparticles were synthesized (AgNPs) using aqueous rhizome extract of Acorus calamus (ACRE) and evaluated their in vitro anticancer activity and in vivo toxicity in a Wistar rat model. The synthesized AgNPs showed good catalytic activity against different organic pollutant dyes. In vitro cytotoxic effects of AgNPs were assessed in Hep2, COLO 205 and SH-SY5Y cells using MTT assay. Further, the apoptotic changes induced by AgNPs in more susceptible Hep2 cells were observed through AO/EB, DCFH-DA, Rhodamine 123, PI/DAPI staining, oxidative stress markers and Western blotting. In vivo toxicity study revealed substantial alterations in the levels of serum biochemical markers including AST, ALT, LDH and inflammatory markers such as TNF-α and IL-6 on day 29 when rats treated with AgNPs as compared to control, however, these levels were restored to normal at the end of washout period on day 89. No remarkable changes were observed in liver oxidative stress enzymes. ICP-OES analysis indicated bio-distribution of silver in spleen (5.67 μg/g) and liver (4.98 μg/g) in rats treated with 10 mg/kg b.w of AgNPs on day 29 and elimination of silver from all organs was observed at the end of washout period on day 89. Histopathological analysis revealed no significant changes in kidney, spleen, lungs, heart, testis and brain with 5 and 10 mg/kg b.w of AgNP. However, 10 mg/kg b.w of AgNPs showed moderate degree of cell swelling and vacuolar degeneration in liver and these alterations were reverted back to normal at the end of washout period. Findings from this study signify green synthesized AgNPs at low concentrations might be useful in many ways with ecofriendly nature. [ABSTRACT FROM AUTHOR]

Ag nanoparticles decorated NiAl-layered double hydroxide/graphitic carbon nitride (Ag/LDH/g-C 3 N 4 ) nanocomposites were synthesized for the first time by an in situ hydrothermal method, followed by photoreduction. The visible-light-driven Ag/LDH/g-C 3 N 4 nanocomposites exhibited enhanced performance for the photocatalytic degradation of aqueous Rhodamine B and 4-chlorophenol. Notably, the Ag/LDH/g-C 3 N 4 nanocomposite with LDH and Ag contents of 15 wt% and 1 wt%, respectively, showed the highest photocatalytic performance, which was far superior to that observed for pure g-C 3 N 4 , LDH, and the binary Ag/g-C 3 N 4 and LDH/g-C 3 N 4 composites. The enhanced photocatalytic efficiency was mainly attributed to rapid charge transfer at the Ag/LDH/g-C 3 N 4 interfaces and the surface plasmon resonance of the Ag nanoparticles, which promotes the separation efficiency of photogenerated charge carriers and improves optical absorption. Additionally, the Ag/LDH/g-C 3 N 4 nanocomposites exhibited excellent photostability during successive experimental runs, with no significant change in degradation performance. These findings are expected to provide new mechanistic insights into the design and construction of efficient visible-light-driven photocatalysts for application in solar energy conversion and environmental remediation. [ABSTRACT FROM AUTHOR]

Discharges in liquid nitrogen between 2 electrodes made of either Cu, Ag or Cu 28 Ag 72 enable the production of several types of comparable nano-objects. First, Cu nanoparticles (NPs) with sizes close to 5 ± 4 nm nm and 40 ± 10 nm are obtained with Cu electrodes and get oxidized in the air to form CuO after liquid evaporation. With Cu 28 Ag 72 electrodes, copper contains a small amount of silver that inhibits oxidation. Next, silver nanoparticles are spherical but when doped with copper, they are facetted. Silver-containing nanowires have very similar features whether they are synthesized with silver or CuAg electrodes. They are made by assembly of NPs. Ag nanosheets are either single crystals in the case of CuAg electrodes or assembly of NPs in the case of silver electrodes. Finally, silver nanorods with traces of copper are only found with CuAg electrodes. Time-resolved optical emission spectroscopy indicates that the optical thickness decreases when copper is added to silver, lines appearing immediately after breakdown and not only after emission of a broad continuum. Emission of lines belonging to the N II system is then observed. The energy deposited being nearly constant, the structure of the discharge is assumed to be changed. [ABSTRACT FROM AUTHOR]

Covalently bound silver nanoparticle (Ag NP)-stacked ultrafiltration membranes were fabricated using carboxylated Ag NPs via amide bond formation. Carboxylated Ag NPs were prepared by a reverse micelle method using 3-mercaptopropionic acid as a NP stabilizer containing carboxyl groups. NP formation was confirmed by transmission electron microscopy and evaluation of the surface plasmon resonance. The thus-prepared spherical and monodisperse Ag NPs were stacked onto an aminated porous aluminum substrate by amide bond formation between the amino groups on the substrate surface and the carboxyl groups on the NP surface via an active ester method. The surface morphology was observed by scanning electron microscopy. To aminate the substrate surface, the substrate was treated with three kinds of aminosilanes. The type of aminosilane affected the NP-stacking behavior. The water permeability and rejection performance of the fabricated NP-stacked substrates as ultrafiltration membranes was evaluated using a cross-flow membrane filtration system. Although the substrate stacked with a single layer of NPs showed only slight rejection performance, that with a multilayer of NPs acted as an ultrafiltration membrane and had a molecular weight cutoff of 500 kDa for dextran. [ABSTRACT FROM AUTHOR]

In this work, sphere-like Ag/Bi 2 O 3 nanocomposites with the average size of ca. 170 nm were successfully synthesized by simple deposition-precipitation method. The antibacterial activities of as-prepared Ag/Bi 2 O 3 nanocomposites were evaluated by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and colony counting methods. It was found that Ag/Bi 2 O 3 nanocomposites displayed greatly improved antibacterial ability against common pathogenic Gram-positive and Gram-negative bacteria in comparison with single-component Bi 2 O 3 nanospheres. More importantly, Ag/Bi 2 O 3 nanocomposites exhibited remarkably outstanding antibacterial activities against clinical drug-resistant bacteria. The antibacterial activity of Ag/Bi 2 O 3 nanocomposite increased with the increase of Ag content and 15 wt% Ag/Bi 2 O 3 nanocomposites showed the highest antibacterial activity. Furthermore, a plausible antibacterial mechanism of Ag/Bi 2 O 3 nanocomposite was proposed. It was believed that the enhanced generation of H 2 O 2 could lead to the membrane leakage of cytosol and the inactivation of respiratory chain dehydrogenaes, which was possibly responsible for the enhanced antibacterial activities of nanocomposites. [ABSTRACT FROM AUTHOR]

Highly uniform reduced graphene oxide/silver nanoparticles binary nanocomposites were successfully prepared using a consolidated dopamine-mediated multistep procedure and a novel ‘green’ one-step solution route mediated itself by graphene oxide. In both nanocomposites, Ag nanoparticles (NPs) with sizes of several nanometers result, anchored on the surface of reduced graphene oxide (rGO) sheets. On the other hand, the one-step procedure allows homogeneously dispersed NPs) on highly exfoliated rGO. The rGO/Ag NP nanocomposites were used as electrode materials for supercapacitors. It was observed that the capacitive performances were markedly affected by the size and dispersion of Ag NPs as well as graphene exfoliation. The one-step synthesized nanocomposite exhibited long stability and specific capacitance as high as 1850 F/g in the voltage range [0 to 1] V and 628 F/g in the voltage range [-0.5 to 0.5] V at a scan rate of 2 mV/s. The excellent capacitive performance can be attributed to the uniform coating of Ag NPs (∼8 nm diameter) on rGO nanosheets in close synergy with rGO resulting in a highly conductive (electrical conductivity up to 1.3 × 10 7  S/m) spongy material. [ABSTRACT FROM AUTHOR]

Biocompatibility and ecotoxicity concerns associated with chemically produced metallic nanoparticles have led to an increasing interest in the development of environmentally benign alternatives for nanoparticle synthesis using biological platforms. Herein, we report the utilization of an extract of seed-derived callus of Catharanthus roseus for the production of stable silver nanoparticles (Ag NPs). The bioreduction of silver ions was evident from UV-Vis spectroscopy results: the absorption maxima were observed at 425 nm, indicative of elemental silver. Transmission electron micrographs revealed that the Ag NPs were well-dispersed and predominantly spherical with particle sizes in the range of 2-15 nm. The synthesized Ag NPs exhibited colloidal stability in an aqueous dispersion for a period of 120 days, as indicated by UV-Vis absorbance spectra and zeta potential measurements. Fourier transform infrared spectroscopy revealed the possible utilization of hydroxyl groups and amides in the reduction of silver ions and surface stabilization of the Ag NPs, respectively. Notably, the synthesized Ag NPs showed considerable antibacterial action against Escherichia coli even after 8 weeks of storage under ambient conditions. Thus, cell extracts of cultured callus of Catharanthus roseus could be explored as an ecofriendly platform for the synthesis of stable and functional nanoparticles. [ABSTRACT FROM AUTHOR]

The anti-infection ability and skin regeneration are important aspects on the progress of wound healing, which needs an ideal wound dressing that not only resists bacteria but also promotes skin regeneration. In this study, zinc oxide/silver/polyvinylpyrrolidone/polycaprolactone (ZnO/Ag/PVP/PCL) nanofibres were prepared through electrospinning. Firstly, zinc oxide nanoparticles (ZnONPs) and silver nanoparticle (AgNPs) were synthesized respectively. Secondly, the two nanoparticles were mixed with polyvinylpyrrolidone (PVP) and polycaprolactone (PCL) to obtain the nanofibres. The results of scanning electron microscopy (SEM) showed that ZnONPs and AgNPs were 40.07 ± 9.70 nm and 37.46 ± 12.02 nm, respectively. After electrospinning, the nanofibres were 368.22 ± 123.96 nm in diameter. Infrared spectroscopy revealed that ZnONPs/AgNPs bimetallic nanomaterials were physically embedded in the nanofibres. The antibacterial effects against Staphylococcus aureus and Escherichia coli of ZnO/Ag/PVP/PCL nanofibres were significantly better than these of the single metal material-loaded nanofibres. More importantly, the combination of ZnO and Ag reduced the cytotoxicity of ZnO/Ag/PVP/PCL bimetallic nanofibres toward fibroblasts. These findings demonstrated that ZnO/Ag/PVP/PCL bimetallic nanofibres should be of greater interest than the single metal nanomaterial-loaded nanofibres in inhibiting growth of bacteria. [ABSTRACT FROM AUTHOR]

We synthesized silver nanoparticles using Rumex hymenosepalus root extract (Rh). Nanoparticles were subjected to a purification process and final product is a composite of Rh and silver nanoparticles (AgNPsC). Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to perform a microstructure study. Additionally, two fractions (RhA and RhB) were obtained from the original extract by filtration with tetrahydrofuran (THF); both fractions were analyzed using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and 2,2-diphenyl-1-picrylhydrazyl (DPPH); total polyphenol content was also determined. Separate inhibition tests for AgNPsC and RhA and RhB were applied to Gram-positive bacteria, Gram-negative bacteria, and yeast (Candida albicans) using the well diffusion method. Extract fractions were found to have inhibitory effects only over Gram-positive bacteria, and silver nanoparticles showed inhibitory effects over all the evaluated microorganisms. Cytotoxicity was evaluated using the tetrazolium dye (MTT) assay in mononuclear peripheral blood cells. In addition, we assessment AgNPsC in THP-1 monocyte cell line, using the cell viability estimation by trypan blue dye exclusion test (TB) and Live/Dead (LD) cell viability assays by confocal microscopy. [ABSTRACT FROM AUTHOR]

Mosquitoes pose a threat to humans and animals, causing millions of deaths every year. Vector control by effective eco-friendly pesticides of natural origin is a serious issue that requires urgent attention. The employment of green-reducing extracts for nanoparticles biosynthesis in a rapid and single-step process represents a promising strategy. In this study, silver nanoparticles (AgNPs) were biofabricated using an essential oil of Aquilaria sinensis (AsEO) and Pogostemonis Herba essential oil of Pogostemon cablin (PcEO) in one step and cost-effective manner. UV-vis spectrophotometry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to confirm the AgNPs formation and their biophysical characterization. The larvicidal and pupicidal toxicity of AsEO, PcEO and biosynthesized AgNPs were evaluated against larvae and pupae of the dengue and Zika virus vector Aedes albopictus. Compared to the tested essential oils, the biofabricated AgNPs showed the highest toxicity against larvae and pupae of Ae.albopictus. In particular, the LC50 values of AsEO ranged from 44.23 (I) to 166 (pupae), LC50 values of PcEO ranged from 32.49 (I) to 90.05(IV), LC50 values of AsEO-AgNPs from 0.81 (I) to 1.12 (IV) and LC50 values of PcEO-AgPNs from 0.85 (I) to 1.19 (IV). Furthermore, histological analysis of the midgut cells of the control and treated larvae exhibited that the epithelial cells and brush border were highly affected by the fabricated AgNPs compared to the essential oils (AsEO and PcEO). Overall, the A. sinensis and P. cablin essential oils fabricated AgNPs have a potential of application as a biopesticide for mosquito control through safer and cost-effective approach. [ABSTRACT FROM AUTHOR]

Biogenic synthesis of silver (AgNPs) and gold nanoparticles (AuNPs) using aqueous extract of Euphrasia officinalis has been reported. Stable AgNPs and AuNPs were formed on adding aqueous solutions of silver nitrate and chloroauric acid with E. officinalis leaf extract, in 19 min and 2 min, respectively. The synthesis method used in present study was simple, reliable, rapid, cost effective and ecofriendly. The synthesized nanoparticles were characterized with field emission transmission electron microscopy (FE-TEM), elemental mapping, selected area diffraction pattern (SAED), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), particle size distribution, zeta potential and Fourier-transform infrared spectroscopy (FTIR). The UV-Vis spectrum confirmed the synthesis of nanoparticles as the absorption band was observed at 450 nm for AgNPs and at 558 nm for AuNPs. The TEM images revealed quasi-spherical shape of AgNPs and AuNPs. The size of nanoparticles was determined to be 40.37 ± 1.8 nm for AgNPs and 49.72 ± 1.2 nm for AuNPs. The zeta potential value demonstrated the negative surface charge and stable nature of nanoparticles. Crystalline nature of the nanoparticles in the face-centred cubic (fcc) structure was confirmed by the peaks in the XRD pattern and SAED pattern. FTIR results showed the functional groups involved in reduction of silver and gold ions to metal nanoparticles. For biomedical application, the nanoparticles have been explored for anticancer, antibacterial and biofilm inhibition activities. It was observed that AgNPs exert anticancer activity against human lung cancer (A549) and human cervical cancer (HeLa) cell lines. On the other hand, AuNPs were able to inhibit only human cervical cancer cells. Furthermore, the AgNPs were active against clinically isolated human pathogens like Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Vibrio parahaemolyticus. Additionally, AgNPs also showed biofilm inhibition activity against S. aureus and P. aeruginosa. [ABSTRACT FROM AUTHOR]

A surface-enhanced Raman scattering (SERS) substrate composed of silver nanoparticles (Ag NPs) was synthesized by spark discharge deposition (SDD). The spark-ablated species were directly deposited on a copper substrate at room temperature and atmospheric pressure. Sharp and reproducible SERRS signals from the model molecule Rhodamine B (Rh B) were observed from the prepared substrates. Under optimized deposition conditions, the detection limit of Rh B reached the single molecular level (1.0 × 10 −16  M) with an enhancement factor of 3.9 × 10 12 . This substrate also provided excellent SERS activity toward crystal violet molecule and the representative biomolecule adenine. We were further interested to find that the activity of the prepared substrate responded very sensitively when we changed the morphology of the deposited NPs by adjusting the operating parameters. An increase in the spark time to 20 min increased the particle size and filling factor, which induced the particles to grow into self-assembled dendrite-like structures. We observed the highest intensity in an Ag NP film with an average particle size of 45 nm and filling factor of 0.57. We speculate that the high sensitivity of this substrate may have derived from the high electromagnetic field produced by the tuning of the particle size and the formation of nanogaps (hot spots) between adjacent particles. This method offers a simple, cost effective, eco-friendly route to the synthesis of highly sensitive, reproducible SERS substrates. [ABSTRACT FROM AUTHOR]

The increasing use of silver nanoparticles (AgNPs) in consumer products, and their resulting influx into wastewater, may pose a threat to biological nutrient removal in wastewater treatment plants. Planktonic ammonia-oxidizing bacteria (AOB), which convert ammonia to nitrite in the first step of nitrification, are highly sensitive to AgNPs and their released silver ions (Ag + ), but the sensitivity of AOB biofilms to AgNPs and Ag + is less clear. This study demonstrated that biofilms of Nitrosomonas europaea , a model AOB, were more resistant to both short-term and long-term exposure to AgNP and Ag + than planktonic cells. The increased resistance of N. europaea biofilms was attributed primarily to the increased biomass and slower growth rates present in the biofilm. Similar inhibition mechanisms were observed for AgNPs and Ag + in both planktonic cells and biofilms with enzymatic inhibition observed at lower concentrations and cell lysis observed at higher concentrations. Long-term continuous exposure to AgNPs lowered the inhibitory concentration by 1–2 orders of magnitude below that required by short-term exposures. Although the total AgNP load was similar between the short and long-term exposure scenarios, the long-term exposure resulted in an order of magnitude more silver being associated in the biofilms and is the primary reason for the increased sensitivity observed. This suggests that short-term batch toxicity assays may greatly underestimate the sensitivity of biofilm treatment systems to long-term exposures of low concentrations of AgNPs and Ag + . [ABSTRACT FROM AUTHOR]

Preparation of Ag nanoparticles with high antibacterial activities and low adverse effects is urgently needed to apply to the medical and consumer products. In this study, a facile, one-step hydrothermal method has been developed to synthesize proanthocyanidins-functionalized Ag nanoparticles in aqueous solution. UV absorption spectra measurement indicated that the obtained Ag nanomaterials are mainly spherical in shape. FTIR results implied that the poly flavonoids moiety of proanthocyanidins have specific interactions with the surface of Ag nanoparticles. HR-TEM and XRD determination revealed that the Ag nanoparticles had a shell-core structure and the Ag core possessed a highly crystalline structure. Antibacterial tests demonstrated that the proanthocyanidins-functionalized-Ag nanoparticles have high bactericidal efficiency against both bacterial and fungus. Further taking into account their excellent stability, the proanthocyanidins-functionalized Ag nanoparticles in present study have the potential to be applied to the products required for the long-acting antibacterial action. [ABSTRACT FROM AUTHOR]

We report the development of a molecularly imprinted polymers–surface-enhanced Raman spectroscopy (MIPs–SERS) method for rapid detection and quantification of a herbicide residue 2,4-dichlorophenoxyacetic acid (2,4-D) in milk. MIPs were synthesized via bulk polymerization and utilized as solid phase extraction sorbent to selectively extract and enrich 2,4-D from milk. Silver nanoparticles were synthesized to facilitate the collection of SERS spectra of the extracts. Based on the characteristic band intensity of 2,4-D (391 cm −1 ), the limit of detection was 0.006 ppm and the limit of quantification was 0.008 ppm. A simple logarithmic working range (0.01–1 ppm) was established, satisfying the sensitivity requirement referring to the maximum residue level of 2,4-D in milk in both Europe and North America. The overall test of 2,4-D for each milk sample required only 20 min including sample preparation. This MIPs-SERS method has potential for practical applications in detecting 2,4-D in agri-foods. [ABSTRACT FROM AUTHOR]

We present one-pot synthesis of silver nanoparticle-decorated reduced graphene oxide (AgNP-rGO) composite by utilizing ascorbic acid as a green reduction agent. The effect of volume ratio between Ag(NH3)2OH complex solution and GO solution was studied. High content of Ag volume seems to slower down the reduction of GO, hence providing high nucleation sites for the Ag ions to be reduced to nanoparticles with much higher density. Meanwhile, due to high reduction rate of GO at low content of Ag volume, it produces less density of nanoparticles with larger particle size. The composite was successfully demonstrated as a low-voltage on-chip photodetector. The presence of high-density AgNPs on rGO results to fast response (393 nA/s) and recovery rate (399 nA/s) with excellent cyclic stability even at low biasing voltage of 1 [V] due to the effective localized plasmon resonance of AgNPs. The detectivity and responsivity remarkably increase with the densities of AgNPs and the biasing voltages, where these values can increase from 3.58 × 105 cm Hz1/2 W−1 and 2.2 × 10−6 A/W at 1 [V] up to 2.12 × 108 cm Hz1/2 W−1 and 3.8 × 10−2 A/W at 20 [V], respectively, for the sample with Ag volume of 75%. [ABSTRACT FROM AUTHOR]

Tungsten trioxide (WO 3 ) nano-material is an indirect band gap semiconductor with gap energy of 2.5–2.8 eV and has multifunctional in electrochromic, optochromic, gaschromic and photocatalytic applications. In this work, we report a novel and facile approach for the direct fabricates the 3D flower-like WO 3 . The WO 3 were assembled from ultrathin nanosheets as the building blocks and the thickness of sheets only have 10 nm and exposed (002) facets on the top and bottom. The as-prepared WO 3 have high special surface area and were employed as scaffolding to deposit the Ag nanoparticles on the surface by the method of in situ redox reaction. The Ag nanoparticles deposition on the surface of WO 3 flowers significant enhances the absorption in visible light by the effect of SPR. The photocatalytic performance of Ag@WO 3 plasmonic photocatalyst is obviously improved when small amounts of Ag particles are deposited on WO 3 photocatalyst surface. This study provided new insights into the fabrication and practical application of high-performance photocatalysts in degrading organic pollutants. [ABSTRACT FROM AUTHOR]

Herein, we report a facile method to synthesize red-emitting, water-soluble Ag nanoclusters (Ag NCs) employing lipoic acid as a stabilizing agent. The Ag NCs show aggregation-induced emission property and have good stability and optical properties. Cu 2+ can disperse the aggregated Ag NCs, accompanied by the quenching of fluorescence. However, the formed Cu 2+ -melamine complex by the coordination chemistry between free copper ion and melamine is able to effectively avoid the quenching process of Cu 2+ to the Ag NCs. Hence, the Ag NCs can be applied to design a novel fluorescent probe based on this property to detect melamine. In the determination of melamine, the as-prepared fluorescent Ag NCs exhibit favorable sensitivity and high selectivity. The limit of detection (LOD) down to 0.022 mg/L and good recoveries of real sample experiments were obtained. This fluorescent probe is proved to be convenient and rapid for detecting melamine, with potential application to trace melamine analysis in complicated samples. [ABSTRACT FROM AUTHOR]

The development of eco-friendly and nontoxic processes for the synthesis of nanoparticles is one of the most important discussed issues in nanotechnology science. This study reports the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of leaf, stem, and root of Avicennia marina, the native and dominant mangrove plant in southern Iran. Among the different plant parts, the extract of leaves yielded the maximum synthesis of AgNPs. Synthesized AgNPs were investigated using UV-visible spectrophotometry, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and Fourier transform infrared (FTIR) spectroscopy. Absorption spectrum in 420 nm confirmed the synthesis of AgNPs. TEM images revealed that the synthesized AgNPs had the same spherical morphology with a size range between 0 and 75 nm. The distribution size histogram indicated that the most frequent particles were in the range of 10-15 nm and the mean size of nanoparticles was 17.30 nm. The results of SEM image showed nanoparticles with a size range between 15 and 43 nm. XRD pattern indicated the crystalline nature of synthesized nanoparticles. EDS results confirmed the presence of elements like silver, carbon, chlorine, nitrogen, and oxygen in the nanoparticles produced from leaf extract. Silver had the maximum percentage of formation, 51.6%. FTIR indicated the presence of different functional groups such as amines, alcohol, alkanes, phenol, alkyl halides, and aromatic loops in the synthesis process. Green biosynthesis of AgNPs using aqueous extract of native A. marina appears rapid, reliable, nontoxic, and eco-friendly. [ABSTRACT FROM AUTHOR]

In the present study, silver nanoparticles (PJB-AgNPs) have been biosynthesized employing Prosopis juliflora bark extract. The biosynthesis of silver nanoparticles was monitored on UV-vis spectrophotometer. The size, charge and polydispersity index (PDI) of PJB-AgNPs were determined using dynamic light scattering (DLS). Different parameters dictating the size of PJB-AgNPs were explored. Nanoparticles biosynthesis optimization studies suggested efficient synthesis of highly dispersed PJB-AgNPs at 25 °C when 9.5 ml of 1 mM AgNO3 was reduced with 0.5 ml of bark extract for 40 min. Characterization of PJB-AgNPs by SEM showed spherical-shaped nanoparticles with a size range ∼10-50 nm along with a hydrodynamic diameter of ∼55 nm as evaluated by DLS. Further, characterizations were done by FTIR and EDS to evaluate the functional groups and purity of PJB-AgNPs. The antibacterial potential of PJB-AgNPs was tested against E. coli and P. aeruginosa. The PJB-AgNPs remarkably exhibited anticancer activity against A549 cell line as evidenced by Alamar blue assay. The dye degradation activity was also evaluated against 4-nitrophenol that has carcinogenic effect. The results thus obtained suggest application of PJB-AgNPs as antimicrobial, anticancer and catalytic agents. [ABSTRACT FROM AUTHOR]

This article reports the utilization of seed extract (GSE) from Gardenia jasminoides Ellis. in the synthesis of silver nanoparticles (Gs-AgNPs) with versatile biological activities. The synthesized Gs-AgNPs were spherical in shape, crystal lattice with an average size of 20 nm as confirmed by UV–vis spectrum, X-ray diffractometer (XRD), Transmission electron microscopy with Energy dispersive X-ray spectroscopy (TEM-EDS) and particle size analyses (PSA). Phenolic compounds, proteins, and terpenoids were likely involved in the Gs-AgNPs synthesis, as indicated by Fourier-transform infrared spectroscopy (FTIR) analysis. The minimum bactericidal concentration (MBC) of the Gs-AgNPs was 12.5 μg·ml −1 for S. enterica Typhimurium and 10 μg·ml −1 for S. aureus . The MBC of the Gs-AgNPs induced >70% bacterial cell death within 60 min, as confirmed by growth curve analysis followed by Confocal laser scanning microscope (CLSM). Gs-AgNPs showed the highest scavenging activity for 1, 2-diphenyl-1-picrylhydrazyl DPPH radical (92.3 ± 0.86%), Nitric oxide (NO) radical (72.5 ± 2.15%), and Hydrogen peroxide H 2 O 2 radical (85.25 ± 1.45%). Anticancer results revealed an IC 50 of 15.625 ± 1.3 μg·ml −1 for Gs-AgNPs, whereas it was 580.54 ± 2.5 μg·ml −1 for GSE. The Gs-AgNPs generated high reactive oxygen species (ROS) resulting in induced apoptosis as evident by up-regulation of apoptosis-related protein. In addition, the photocatalytic results revealed about 92% of the reduction in Coomassie Brilliant Blue dye color with Gs-AgNPs. Hence, this work provided economically viable and ecologically sustainable Gs-AgNPs as an alternative biomaterial for future therapeutic applications as antimicrobial, antioxidant, anti-cancer agents and in dye degradation for water remediation. [ABSTRACT FROM AUTHOR]

The present study was aimed to investigate the antibacterial efficacy of fucoidan mediated silver nanoparticles (Fu-AgNPs) synthesized from Spatoglossum asperum . The synthesized Fu-AgNPs were characterized by UV–visible, Field emission - scanning electron microscope (FE-SEM), Tranmission electron microscope (TEM), X-ray diffraction (XRD), Selected area electron diffraction (SAED) pattern, Energy-dispersive X-ray spectroscopy (EDAX), Fourier transform infrared spectroscopy (FT-IR), Dynamic light scattering (DLS) and Zeta potential analysis. The UV–visible spectrum of Fu-AgNPs exhibited a characteristic surface plasmon resonance (SPR) peak at 440 nm. The electron microscopic results revealed that the nanoparticles were spherical to oval in shape and are found to be 20 to 46 nm. Altogether the X-ray diffraction analysis showed that the Fu-AgNPs were crystalline in nature. The FT-IR spectrum confirmed the existence of C C stretching vibration of aromatic compounds and sulfated groups of fucoidan plays a major role in the synthesis of Fu-AgNPs. The biosynthesized Fu-AgNPs shows potential antibacterial activity against Klebsiella pneumoniae in agar bioassay, disk diffusion, reactive oxygen species, protein leakage and confocal laser scanning microscopy assays. Furthermore, Artemia toxicity assay results showed less mortality (3.3 ± 0.8%) even at higher concentration of Fu-AgNPs. Therefore, Fu-AgNPs can be effectively used as an antibacterial agent in the pharmaceutical fields. [ABSTRACT FROM AUTHOR]

Silver (Ag) and Titania (TiO 2 ) nanoparticles (ATNPs) co−embedded and dysprosium (Dy 3+ ) ions doped magnesium−zinc−tellurite glasses were synthesized via melt quenching method. As−prepared samples were characterized using various analytical tools. Nanoparticles concentration dependent spectroscopic properties of the prepared glasses were evaluated using Judd−Ofelt (J−O) analysis. XRD pattern verified the amorphous nature of as−quenched samples. The UV–Vis spectra revealed six absorption bands centred at 1690, 1283, 1097, 904, 800 and 755 nm, assigned to the transitions from the ground level to different excited levels of Dy 3+ ions. The photoluminescence (PL) emission spectra of the glass system displayed three emission bands positioned at 482 (blue: 4 F 9/2  →  6 H 15/2 ), 574 (yellow: 4 F 9/2  →  6 H 13/2 ) and 664 nm (weak red: 4 F 9/2  →  6 H 11/2 ). For all the bands, the PL intensities of the studied glasses were more pronounced than singly embedded sample (either ANPs or TNPs). Furthermore, the enhancement in the PL peak intensity due to the inclusion of metallic NPs was attributed to the surface plasmon resonance mediated local field effect in the proximity of Dy 3+ ions. Ligand bonding of Dy 3+ showed the ionic nature of the prepared glasses. The absorption and emission spectral data were used to evaluate the J−O intensity parameters (Ω λ (λ = 2, 4, 6)) and radiative properties. Values of Ω λ (λ = 2, 4, 6) for glass with 0.1 mol% of TNPs exhibited the trend of Ω 2 >Ω 6 >Ω 4 while all other glasses revealed Ω 2 >Ω 4 >Ω 6 . It was demonstrated that by combining two types of NPs (Ag and TiO 2 ) hot spot with intense electromagnetic field could be created in the neighbourhood of Dy 3+ ion to achieve enhanced optical attributes of the proposed glasses. The attainment of large quality factors and quantum efficiency (≈100%) in the ATNPs co−embedded glasses were established to be beneficial for the development of solid state lasers and other photonic devices. [ABSTRACT FROM AUTHOR]

ABSTRACT: Bifunctional nanofiber mats consisting of chitosan (CS), poly(vinyl alcohol) (PVA), and silver nanocrystals (Ag NCs) have been fabricated by a facile electrospinning method. The formation and presence of Ag NCs supported on CS/PVA nanofibers are confirmed by ultraviolet‐visible spectroscopy and X‐ray diffraction. The morphology of the samples is characterized by transmission electron microscopy and scanning electron microscopy. The prepared Ag NCs/CS/PVA nanofiber mats show pronounced antibacterial activity against Escherichia coli and excellent filtration property for suspended particulate matter (SPM) particles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46504. [ABSTRACT FROM AUTHOR]

The dielectric properties of poly(vinylidene fluoride) (PVDF) polymer incorporating with silver (Ag) nanoparticles, which were successfully prepared via a hydrothermal method using Aloe vera plant–extracted solution as surface stabilizer and reducing agent (Ag@Ale–NPs), were investigated. Ag@Ale–NPs/PVDF polymer nanocomposites were prepared by a liquid–phase assisted dispersion and hot–pressing methods. The microstructures of the Ag@Ale–NPs and Ag@Ale–NPs/PVDF nanocomposites were characterized. The modification of the Ag@Ale–NPs surface was confirmed using X–ray photoelectron spectroscopy. Interestingly, by using a filler volume fraction of 0.18, the composite exhibited a high dielectric permittivity of ≈92.5 with very low loss tangent of 0.049 at room temperature and 1 kHz. With further increasing a filler volume fraction to 0.22, a greatly enhanced dielectric permittivity of ≈257.2 was obtained with low loss tangent (tan δ ≈ 0.26). Excellent dielectric properties of the Ag@Ale–NPs/PVDF nanocomposites were described by the interfacial polarization effect and the formation of micro–capacitor in the PVDF polymer matrix. [ABSTRACT FROM AUTHOR]

Paper-based SERS sensor has attracted considerable attention recently, resulting from the separation, aggregation and high sensitive detection of biomolecules. However, optical losses, caused by the holes or “vase”-like defects, affect the overall intensity of the electromagnetic (EM) coupling and then the Raman signal. Silver nanoflowers (AgNFs) connected with silver nanoparticles (AgNPs) arrays are proposed and firstly obtained onto such “vase” surface to enhance the EM coupling. AgNFs are easily self-assembled on the defects, and the closed packed AgNPs can be formed on the other area. Multiple cascaded amplification mechanisms (localized surface plasmon mode and optical standing waves or refraction) are used to promote the EM magnification. Such paper card is also exploited successfully as an integrated platform, allowing for ultra-sensitivity (1 × 10 −19 M) CV and (1 × 10 −20 M) R6G detection. [ABSTRACT FROM AUTHOR]

Asymmetrical etching of nanoparticles was achieved by employing interface-confined galvanic replacement reactions. Interfacial Ag nanocubes, nanowires and nanospheres were fabricated into symmetry-reduced cubic, trough-like and spherical nanocups, respectively. The formation of nanocups is attributed to in situ local nanomasking and selective etching of interfacial nanoparticles at the single-nanoparticle level. [ABSTRACT FROM AUTHOR]

Constructing a 0D/2D heterojunction is an important way to ameliorate the charge separation for achieving efficient solar hydrogen production. In this study, zero-dimensional (0D) AgIn 5 S 8 nanoparticles/two-dimensional (2D) layered ZnIn 2 S 4 0D/2D heterojunction composite was designed and prepared via a facile two-step hydrothermal process. Anchoring the AgIn 5 S 8 nanoparticles on the 2D layered ZnIn 2 S 4 can shorten the charge-migration distance, provide abundant active sites and extend the visible-light absorption. Benefiting from those favorable properties, the AgIn 5 S 8 /ZnIn 2 S 4 0D/2D heterojunction composite exhibits the highest H 2 evolution rate of 949.9 μmol g −1  h −1 under visible light irradiation (λ > 420) when the weight ratio of AgIn 5 S 8 to ZnIn 2 S 4 is 30%, which is about 3.6 and 17.6 times higher than pure ZnIn 2 S 4 and AgIn 5 S 8 , respectively. Photoluminescence (PL) and photocurrent response results indicate that the improved charge separation efficiency is a critical reason for the enhanced H 2 evolution activity. This study suggests that constructing a 0D/2D heterojunction can provide an efficient way to improve the photocatalytic performance of semiconductor photocatalysts for solar hydrogen production. [ABSTRACT FROM AUTHOR]

Silver nanoparticles exhibit a powerful antimicrobial action showing a pronounced potential to be widely used against drug resistance bacteria. The present work describes the optical properties and antimicrobial effect of silver nanoparticles produced by femtosecond laser photoreduction of AgNO 3 in the presence of tryptophan water solution. The advantages of this method are the absence of hazardous chemical reducing agents in the solution, and the versatile dimensional control achieved. The synthesized silver nanoparticles were characterized by absorption and fluorescence spectroscopy and their antibacterial activity were determined by monitoring the cell viability of Escherichia coli . The effects of the silver nanoparticles concentration and laser parameters (exposure time and pulse energy), on the formation of the nanoparticles, and its influence on the bacteria growth inhibition were studied. The prepared silver nanoparticles exhibited suitable antimicrobial properties. The results demonstrated that the nanoparticles concentration plays an important role in their bactericidal efficacy. The increase in the laser energy caused an increase in E. coli growth inhibition. Irradiations with energies around 300 μJ for 60 min presented high antimicrobial activity due to the presence of kynurenine, sub product of tryptophan photolysis. The first-time formation mechanism of tryptophan silver nanoparticles in high optical intensities was also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Curcumin‐functionalized Ag/Ag2O (c‐Ag/Ag2O) nanocomposites with varying proportions of curcumin and Ag/Ag2O were prepared by a simple one pot green synthesis protocol in aqueous medium. The plasmonic band undergoes slight redshift, broadening and decrease in intensity with increase in the proportion of Ag2O formed. These composite nanoparticles were found to be efficient visible‐light photocatalysts for aerobic oxidation of methyl orange and rhodamine B (RhB). Functionalization by curcumin significantly enhanced the photocatalytic activity with good reusability. The photocatalytic oxidation rate showed super linear increase with light intensity because of localized surface plasmon resonance (LSPR)‐induced strong near field. The trapping experiments confirmed that superoxide radicals were the main active species responsible for the degradation reaction. A plasmonic Z‐scheme photocatalytic mechanism is proposed to explain the possible charge transfer and separation behavior of electron–hole pairs among Ag, Ag2O and curcumin under visible‐light irradiation. [ABSTRACT FROM AUTHOR]

Present work covers the state-of-art progress in the advanced nanoarchitecture of organic-inorganic hybrid material; a starting material for the antimicrobial filter. TEMPO-mediated oxidation of microfiber cellulose was carried out to introduce the surface active carboxyl groups. Accordingly, qualitative and quantitative substitution of a functional group was investigated using FTIR, Solid state 13 C CP/MAS NMR , and potentiometric titration; the reaction resulted to about 21.06% increase in carboxylate content. Further, the microwave irradiated (600 W) in-situ synthesis of AgBr and AgCl nanocubes were prepared and doped on carboxylated microfiber. The prepared AgBr@TO-MF and AgCl@TO-MF were tested using XRD, XPS, SEM and FTIR. With an average size of AgBr and AgCl nanocubes of around 200 ± 28 nm and 116 ± 10.73 nm. Whereas, AgBr@TO-MF and AgCl@TO-MF shown excellent antimicrobial activity against E. Coli and B. Subtilis , with MIC at around 200 μg/mL and 150 μg/mL, respectively. Fascinatingly, ICP-OES analysis estimated the silver leached was around 0.1 ppm. [ABSTRACT FROM AUTHOR]

Antimicrobial cotton textiles were fabricated via green synthesis of silver nanoparticles (AgNPs) from silver nitrate, using whey protein isolate (WPI) as both reducing agent and stabilizer. Natural tannin-rich extract from Xylocarpus granatum bark (XGBE) was used to form insoluble complexes with the WPI through hydrogen bonding and hydrophobic forces. Cotton fabrics were coated using one-step padding of the AgNP/WPI/XGBE mixture, followed by air drying. Both WPI and XGBE served as an excellent natural binder for AgNPs with cotton. Transmission electron microcopy showed the AgNPs to be almost spherical, with a mean diameter of 31 nm. Antimicrobial treatment did not significantly alter the original color of the fabrics at low AgNPs loadings. The coated fabrics showed strong and durable antibacterial activity against Staphylococcus aureus and Escherichia coli , with 99.99% bacterial reduction. Treatment with only 50 ppm of silver nitrate and WPI maintained more than 90% bacterial reduction after 50 washing cycles. In a test of antifungal properties, at least 203 mg silver per kilogram of fabric was required to suppress the growth of Aspergillus niger . In-vitro cytotoxicity testing demonstrated the antimicrobial treated fabrics to be non-toxic to L929 cells. Antimicrobial treatment did not have significant negative effects on the drapeability and tearing strength of the fabrics. This approach is very attractive in terms of the safety and biocompatibility of the raw materials, the simplicity of the synthesis and the coating process, and the antimicrobial effectiveness of the treated fabrics. [ABSTRACT FROM AUTHOR]

Bio-nanotechnology is a rapidly growing scientific field of producing Nano sized particles by using biological systems. In this study the biosynthesis of silver nanoparticles (Ag NPs) using leaf extract of Satureja hortensis treated with different concentration of NaCl (0, 50, 100 and 150 μM) was reported. In addition, the nanoparticles were assessed against two gram-positive and one gram-negative bacteria. The biosynthesized Ag NPs were characterized using FESEM, XRD, UV/vis spectroscopy and related to the size, shape and morphology of the nanoparticles as revealed by FESEM. FTIR spectrum indicated various functional groups effective on Ag NPs biosynthesis. In each treatment, the plant extract showed color change from yellow to brownish-red after Ag NPs biosynthesis. The surface Plasmon resonance found at 450 nm confirmed the formation of Ag NPs. The highest rate of Ag NPs biosynthesis was related to 150 μM treatment. FESEM images revealed relatively spherical shape ranged from 2.9 to 3.4 nm. FTIR results expounded the functional groups of plant extract responsible for the bio-reduction of silver ions and their interaction between them. Ag NPs biosynthesis by 150 μM treatment showed the smallest size (2.9 nm) and thus the most antibacterial activity especially against Bacillus subtilis . Our results revealed that aromatic bicyclic monoterpenes have the most effective role in the biosynthesis process in 150 μM treatment. To the best of our knowledge no similar study has been reported. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) are widely used in various fields but their physical and chemical instability have limited their applications. The present work demonstrates a novel approach for the synthesis and stabilising of AgNPs. Chitosan and carboxymethyl β-cyclodextrin were used to prepare a polymeric hydrogel with glutaraldehyde as cross-linker. As a result, AgNPs were formed with very high dispersion and stability in the hydrogel structure. It is possible to create nanoreactors to produce AgNPs by adding CM-βCD to the structure of the hydrogel. Fourier transform infrared (FTIR) analysis was employed to characterise the Cs-CM-βCD hydrogel. The morphologies of pure Cs-CM-βCD hydrogel and silver nanocomposite were observed by scanning electron microscopy. Moreover, UV-VIS spectroscopy and X-ray diffraction were used to characterise the prepared silver nanocomposite. In addition, the antibacterial properties of these silver nanocomposite hydrogels were investigated against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). [ABSTRACT FROM AUTHOR]

Abstract: This study demonstrates the bottom‐up synthesis of silver nanolenses. A robust coating protocol enabled the functionalization of differently sized silver nanoparticles with DNA single strands of orthogonal sequence. Coated particles 10 nm, 20 nm, and 60 nm in diameter were self‐assembled by DNA origami scaffolds to form silver nanolenses. Single molecules of the protein streptavidin were selectively placed in the gap of highest electric field enhancement. Streptavidin labelled with alkyne groups served as model analyte in surface‐enhanced Raman scattering (SERS) experiments. By correlated Raman mapping and atomic force microscopy, SERS signals of the alkyne labels of a single streptavidin molecule, from a single silver nanolens, were detected. The discrete, self‐similar aggregates of solid silver nanoparticles are promising for plasmonic applications. [ABSTRACT FROM AUTHOR]

Chitosan-based hydrogels with stabilized Ag nanoparticles were synthesized in the aqueous solutions of carbonic acid, i.e. water saturated with CO 2 under pressure in hundreds of bars. Such a medium is biocompatible and self-neutralizing at decompression. The influence of various parameters, such as chitosan molecular weight, molar ratio of chitosan to silver, additional stabilization of gels by genipin as a cross-linking agent, on the structure of the chitosan/Ag composites was investigated using transmission electron microscopy, scanning electron microscopy, X-ray diffraction analysis, rheology measurements. The distributions of chitosan-stabilized Ag nanoparticles in a chitosan matrix turned out to be uniform, their average size was in the range of 2–5 nm. The higher degree of Ag nanoparticles reduction could be achieved using self-eliminating gaseous hydrogen as an additional reducing agent being admixed to CO 2 . This was consistently confirmed by different research methods (TEM, XRDA, UV–vis spectroscopy). [ABSTRACT FROM AUTHOR]

Novel ternary composite reduced-graphene oxide/Ag nanoparticles/poly( p -phenylenediamine) (rGO/Ag NPs/P p PD, GMP) is first designed, synthesized and demonstrated. Nanocomposite rGO/Ag NPs is prepared by in situ simultaneous reduction of [Ag(NH 3 ) 2 ] + and GO, and then a thin layer of P p PD is coated on the surface of ternary composite by polymerization. In this study, Ag NPs are no longer just designed as a typical dopant to improve conductivity, but can contribute the pseudocapacitance for composite. As a result, the obtained composite GMP-1,5,4 delivers an excellent areal capacitance of 2779 mF cm −2 (926 F g −1 ) at 1 mA cm −2 and a good rate capability (1639 mF cm -2  at 40 mA cm −2 ). Meanwhile, the design of composite is indeed an effective strategy for combating the low cycling stability. For comparison, GMP-1,5,4 maintains 89.42% of the initial specific capacitance after 2000 cycles, while only 52.24% for GM-1,5 is left after 500 cycles. Additionally, it is found that ammonium persulfate (APS), a typical initiator for polymerization, may oxidize Ag NPs when its concentration is low. Therefore, our study will be of great help to researchers who will synthesize polymer/Ag NPs composite in the future. [ABSTRACT FROM AUTHOR]