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The surface plasmon resonance property of silver nanoparticles (AgNPs) makes them a top-notch material for developing sensors, especially in surface-enhanced Raman scattering (SERS). The multi-shape silver nanoparticles decorated on cellulose fiber of paper provide flexible paper-based SERS substrates with different sensitivity. The isotropic and anisotropic morphology of AgNPs on filter paper has been controlled by weak and strong reducing agents: sodium borohydride (NaBH4), ascorbic acid (L-AA), glucose, formaldehyde (HCHO). The capping agent's chitosan and the reaction conditions like the ratio of precursors and stirring speed also influence the shape, size, stability, and dispersity of AgNPs on filter paper. Multi-shape AgNPs on paper are obtained as spherical shapes (about 50–100 nm), rods (size 100–500 nm in length, 50-nm wide), or thin wings. Depending on the reduction condition, these AgNPs can be single-dispersed or stuck together to form corals on paper. The fabricated paper-based SERS substrates were investigated the optical characterization and used to detect melamine in an aqueous solution with detection limits as low as 10−8 M with the EF = 2.3 × 109. [ABSTRACT FROM AUTHOR]

This work presents attempts to synthesize silver-doped copper nitride nanostructures using chemical solution methods. Copper(II) nitrate and silver(I) nitrate were used as precursors and the oleylamine as a reducing and capping agent. Homogeneous Cu3N/Ag nanostructures with a diameter of ~ 20 nm were obtained in a one-pot synthesis by the addition of the copper(II) salt precursor to the already-synthesized silver nanoparticles (Ag NPs). Synthesis in a two-pot procedure performed by adding Ag NPs to the reaction medium of the Cu3N synthesis resulted in the formation of a Cu3N@Ag nanocomposite, in which Ag NPs are uniformly distributed in the Cu3N matrix. The morphology, structure, and chemical composition of the obtained specimens were studied by TEM, XRD, XPS, and FT-IR methods, while optical properties using UV–Vis spectroscopy and spectrofluorimetry. The band gap energy decreased for Cu3N/Ag (Eg = 2.1 eV), in relation to pure Cu3N (Eg = 2.4. eV), suggesting the insertion of Ag atoms into the Cu3N crystal lattice. Additionally, Cu3N and Cu3N/Ag nanostructures were loaded on graphene (GNP) and tested as a catalyst in the oxygen reduction reaction (ORR) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The Cu3N/Ag-modified GNP hybrid material revealed catalytic activity superior to that of Cu3N-based GNP hybrid material and pure GNP, comparable to that of a commercial Pt/C electrode. [ABSTRACT FROM AUTHOR]

Nickel nanoparticles are an attractive ingredient for preparing metal-based conductive pastes. In particular, using a mixture of nanoparticles containing two different particle sizes as the paste fillers is an effective way to improve the microstructure as well as the electrical conductivity of the printed films after sintering. This study presents a facile solvent-directed chemical reduction method for the synthesis of nickel nanoparticles with bimodal size distribution in one-pot. Through simply adjusting the volume ratio of alcohol (methanol, ethanol or n-propanol) to water and nickel precursor concentration in a mixed solvent system (alcohol and water), the size and size distribution of the synthesized nickel nanoparticles could be controlled. The bimodal nickel nanoparticles obtained at a volume ratio of methanol to water of 2 were used as fillers for a screen-printing paste. After sintering at a temperature of 600 ℃, the printed film exhibited a compact structure with a relatively low volume resistivity of 167.3 µΩ∙cm. [ABSTRACT FROM AUTHOR]

The current study aimed to investigate the antibacterial activity of different anisotropic structures of silver nanoparticles in the hexagon and spherical shapes against MDR-bacteria isolated from water sources in Egypt. The water samples collected from four different dairy farm-related sites were tested bacteriologically, followed by identification of the antibiotic-resistant profile for the isolates. The result revealed that Enterococcus spp, Proteus spp, and E. coli spp are the most common organisms in all tested water samples, and the antibiotic-resistant profile identified 11/13 waterborne isolates as MDR-bacteria. Herein, spherical and hexagonal silver nanoparticles were prepared with an average size of 26 ± 6 nm and 375 ± 80 nm, respectively, through the chemical reduction method. Further, MDR gram-positive (Enterococcus) and MDR gram-negative (E. coli) were selected for studying the antibacterial property of the synthesized AgNPs using agar well diffusion method. In another experiment, microdilution broth assay coupled with XTT assay is optimized for facilitating the testing of a broad range of AgNPs concentrations efficiently without the need for laborious preparation of the colony counting method. Our results indicated that AgNPs in spherical and hexagonal shapes are potent antibacterial against the MDR-waterborne bacteria in a dose and shape-dependent manner. The hexagonal AgNPs (h-AgNPs) express higher bactericidal activity when compared to spherical AgNPs (AgNSs) against the two tested MDR-bacteria, but the E. coli isolate more sensitive to both tested shapes of AgNPs than the Enterococus isolate. The results recommend that AgNPs can be used as efficient growth inhibitors for water-borne bacterial pathogens, making them applicable to various water filters and antimicrobial applications. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (GNPs) are forecasted to provide an attractive platform in biomedicine and catalysis with their potentials of combining a variety of biophysicochemical properties into an integrated nanodevice with great therapeutic and optical functions. There are several reports of crude plant extracts mediating the conversion of metal ions into nanoparticles. However, we aimed to investigate the capability of single bioactive compounds, namely ginsenosides compound K (C-K) and Rh2, to accommodate a synergistic chemical reduction of gold salts by one-pot green chemistry. Ginsenosides C-K and Rh2 are unique triterpenoid saponins present in Panax ginseng Meyer, a perennial plant traditionally used as an oriental medicinal herbal with long history. C-K and Rh2 have demonstrated diverse pharmacological properties such as anticancer, anti-inflammation, anti-aging, and neuroprotective properties. The reduction of gold ions by these ginsenosides led to the production of nontoxic GNPs as tested in mouse macrophage (J774A.1) and human kidney epithelial (HEK-293) in vitro. The kinetics of the bioreduction and the influence of pH were examined by an ultraviolet-visible (UV-Vis) spectrophotometer. GNPs were characterized by field emission transmission electron microscopy (FE-TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. Ginsenoside loading efficiency of C-K-GNPs and Rh2-GNPs was determined to be approximately 62.83% and 54.91%, respectively, by thermogravimetric analysis (TGA). These results suggest that one-pot synthesis by ginsenosides C-K and Rh2 may be useful for producing ginsenoside-loaded gold nanocarriers. [ABSTRACT FROM AUTHOR]

Herein, six kinds of PdNPs (including icosahedron, sphere, spindle, cube, rod, and wire) were synthesized via simple methods. The catalytic activities were investigated by the reduction reaction of Cr(VI) and Suzuki coupling reaction. Chemically synthesized morphologies of the six catalysis were characterized by transmission electron microscopy, field emission scanning electron microscopy, and X-ray diffraction, etc. Pd icosahedron shows a better catalytic property than other PdNPs with a rate constants 0.42 min for the reduction of Cr(VI). Moreover, the electrocatalyst shows that Pd icosahedron possesses a bigger surface area of 8.56 m/g than other nanoparticles, which is attributed to the better catalyst. The Pd icosahedron possesses a better catalytic property, attributing to the abundant exposed {111} facets with high activity on Pd icosahedron. The catalytic activities are closely related to the surface area with the following order: icosahedrons ≥ sphere > rod > spindle > cube > wire. The Pd icosahedron catalyst represents a strong activity for Suzuki coupling reaction as well, outweighting is 80%. The results reveal that Pd icosahedron acts as an efficient catalyst compared to other PdNPs (wire, rod, sphere, spindle, and cube). [ABSTRACT FROM AUTHOR]

Multifunctional silica gel with embedded silver nanoparticles (SiO-AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO-AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO bulk. Synthesis of AgNP directly to the SiO matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO concentration used during the SiO-AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO-AgNP with optimal composition was around 10. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations. [ABSTRACT FROM AUTHOR]

Gold nanoparticles are one of the most used nanomaterials. They are usually synthesized by the reduction of gold(III) chloride. However, the presence of halide ions in the reaction mixture is not always welcome. In some cases, these ions have detrimental influence on the morphology and structure of resulting nanoparticles. Here, we present a simple and halogen-free procedure to prepare gold nanoparticles by reduction of gold(III) oxide in neat oleylamine. The method provides the particles with an average size below 10 nm and dispersity of tens of percent. The process of nanoparticle formation was monitored using UV-Vis spectroscopy. The structure and chemical composition of the nanoparticles was determined by SEM, XPS and EDX. We also proposed the mechanism of reduction of gold(III) oxide based on MS, IR and NMR data. Importantly, the synthetic protocol is general and applicable for the preparation of other coinage metal nanoparticles from the corresponding metal oxides. For instance, we demonstrated that the absence of halogen enables efficient alloying of metals when preparing gold-silver bimetallic nanoparticles. [ABSTRACT FROM AUTHOR]

In order to clarify the effect of reduction enhancer on the nanoparticle formation process and their structural and catalytic properties, carbon-supported Pt-Cu nanoparticles were synthesized by electron beam irradiation on an aqueous precursor solution in the presence/absence of reduction enhancer. In the absence of reduction enhancer, tetravalent platinum oxide particles of approximately 1 nm in diameter were formed on carbon support with copper barely precipitated, while in the presence of 2-propanol or ethylene glycol or glucose both platinum and copper precipitated as few-nanometer-sized alloy particles together with copper oxides. It was suggested that the metal nuclei produced upon electron beam irradiation do not have enough lifetime without reduction enhancer due to fast oxidation of the nuclei by oxidizing radicals, while the reduction enhancer scavenges these oxidizing radicals preventing oxidation of metallic clusters and prolonging their lifetime. Ethylene glycol gave smaller and better alloyed particles with less copper oxides compared to 2-propanol since the carbonyl compounds derived from oxidation of ethylene glycol protect metallic clusters from oxidation further prolonging their lifetime. In the electrochemical measurements, the methanol oxidation activities of Pt-Cu/C catalysts were well explained by their structural characteristics. [ABSTRACT FROM AUTHOR]

Colloidal nanoparticle assemblies (NPAs) were obtained in a one-step procedure, by reduction of HAuCl by hydroxylamine hydrochloride, at room temperature, without the use of any additional nucleating agent. By changing the order of the reactants, NPAs with mean size of ~20 and ~120 nm were obtained. Because of their size and irregular popcorn like shape, the larger size NPAs show absorption in the NIR spectral region. The building blocks of the resulted nanoassemblies are spherical nanoparticles with diameters of 4-8 and 10-30 nm, respectively. Moreover, by stabilizing the colloid with bovine serum albumin at different time moments after synthesis, NPAs of controlled size between 20 and 120 nm, could be obtained. The NPAs were characterized using UV-Vis spectroscopy, TEM and SEM electron microscopies. In addition, the possibility of using the here proposed NPAs as surface-enhanced Raman scattering (SERS) substrate was assessed and found to provide a higher enhancement compared to conventional citrate-reduced nanoparticles. [ABSTRACT FROM AUTHOR]

Potassium-type birnessite and lithium-containing manganese oxides were prepared by the polyol process. The Mn(III)/Mn(IV) mixed-valencies compounds are obtained through the controlled reduction of potassium permanganate in a basic water-diethylene glycol mixture at moderate temperature and very short reaction time, 70 °C and 10 min, respectively. Both solids are quite well crystallized and display high specific surface areas, 137 and 329 m g, respectively. Several polyols with variable chain lengths have been used and it is shown that the nature of the polyol has a marked influence on the textural properties of the birnessite-type solid. [ABSTRACT FROM AUTHOR]

The magnetic behavior of very fine metallic Ni (Ni) particles dispersed in a matrix of 10 % by mol (m/o) YO-stabilized ZrO (10YSZ) was examined. Specimens that nominally contained 0.1, 0.5, and 1 m/o Ni were prepared by a high-purity chemical synthesis method followed by a reduction treatment in H. A 0.5 m/o Ni specimen was also made by heating in vacuum, within a carbon environment. dc and ac susceptibility measurements revealed the presence of superparamagnetic Ni as well as Ni. A Stoner-Wohlfarth formulation was applied to determine that the average Ni particle size was between 4 and 7 nm, and this was confirmed by transmission electron microscopy. The activation energy for single-domain particle spin reversal and K, the effective anisotropy constant, were determined. K was higher for the vacuum heat treatment specimen because it contained less residual organic material, and therefore a higher density of Ni particles. It is shown that it is possible to make very fine Ni particles in YSZ via a direct conversion from Ni nitrates. [ABSTRACT FROM AUTHOR]

Flat Ag nanoflowers were directly synthesized from the bioreduction of AgNO using Flos Magnoliae Officinalis extract without any additional stabilizer or protective agent at room temperature. Effects of concentrations of the Flos Magnoliae Officinalis extract on the Ag nanostructures were investigated. The main components containing flavone, polyphenol, protein, and reducing sugar in the plant extract were thoroughly determined before and after the reaction, and the dialysis experiments were also conducted. The results of components analysis and dialysis showed that gallic acid representing polyphenols played an important role in the biosynthesis of silver nanoplates. Trisodium citrate combined gallic acid solution, instead of Flos Magnoliae Officinalis extract, was employed and successfully simulated the biosynthesis process of the flat Ag nanoflowers. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A facile chemical process has been developed for the preparation of magnetic FeCo nanoparticles. The FeCo nanoparticles were mono-dispersed, obtained by the safe and ecofriendly method, possessed saturation magnetization up to 187 emu/g, and demonstrated excellent chemical stability. In this work, we have studied how to control Fe/Co ratio by variation of precursor ratio, and how to vary particle size from 9.3 to 12.3 nm by surfactant amount used. The cytotoxicity of as-synthesized nanoparticles was investigated after coating with the poly(methyl methacrylate-co-butyl acrylate) by the emulsion process and the results demonstrated high biocompatibility. Similarly, the same synthesis method was used with the single precursor FeO(OH) or CoO. The results showed that this method can also fabricate 10 nm mono-dispersed spherical FeO particles and self-assembly Co nanoneedles. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene aerogels-supported NiS nanoparticles (NiS/NG) were synthesized by a one-pot hydrothermal method. In the process, l-cysteine was used not only as the nitrogen source to form the nitrogen-doped graphene aerogels, but also the sulfur source to form NiS. The nitrogen-doped graphene (NG) hybrids show an interconnected reticulation of NG sheets with uniform deposition of NiS NPs, and the NiS NPs are deposited on the NG layers. In studying the effects of the NG and NiS/NG for the ORR, we found that NiS/NG shows a more positive onset potential, higher current density, and higher electron transfer number (∼4) for the oxygen-reduction reaction (ORR) in alkaline media than NG. Furthermore, NiS/NG shows better durability and methanol tolerance than the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

The effects of phosphorus (PHO) and copper (Cu) additions to the aqueous precursor solution on the structure of Pt-Cu nanoparticles were investigated for a radiation-induced reduction method. Addition of PHO in the precursor solution reduced the diffraction intensity of Pt or Pt-Cu crystallites due to smaller size and/or lower crystallinity. Both the diffraction intensity and the particle size (measured by an electron microscope) were minimized when Cu/Pt ratio was 0.05-0.25, which was attributed to the effects of copper and phosphorus to stabilize crystallites and particles through the negative heat of mixing. The concomitant increase in phosphorus content suggested that PHO is partly reduced and taken into the Pt lattice. Further increase of copper content caused larger particles and decrease in phosphorus content. These trends were also consistent with electrochemical surface area and oxidation/reduction behavior of Pt surface. The radiation-induced reduction method is suited to produce small Pt-Cu particles uniformly distributed on carbon support, which are potentially served for heat treatment for improved oxygen reduction performance. [ABSTRACT FROM AUTHOR]

The synthesis of silver nanoparticles has been investigated using Ag(CN) species as precursor, citrate ions as reducing agent, and dodecyl sulfate ions as stabilizer, at pH 11 and 97 °C, in a batch stirred glass reactor. The role of Cu ions in the synthesis was also studied. Bird- of- paradise flower-type nanostructures composed of AgCN nanowires having inside Ag and AgCN nanoparticles were produced in the absence of Cu ions. The nanostructures slowly grew and transformed to AgCN nanowires with embedded Ag and AgCN nanoparticles, having a mean size of 9.7 ± 3.6 nm. The presence of Cu ions in the synthesis significantly enhanced the production of the nanostructures. Nanowires having a thickness of 63 ± 33 nm and length of up to 20 μm were produced. Cu ions also simultaneously lead to the synthesis of ordinary free Ag nanoparticles with a bimodal size distribution (mean sizes of 9.9 ± 3.9 and 65.5 ± 27 nm) and a low experimental formation kinetic rate constant of 1.22 × 10 s. Feasible mechanisms are presented for the origin of the AgCN nanowires, Ag and AgCN nanoparticles inside the nanowires, and for the free Ag nanoparticles. UV/Vis spectrometry was used to measure the surface plasmon resonance of the nanoparticles and the synthesis kinetic rate constant of the free Ag nanoparticles. ATR-FTIR spectroscopy, EDS-SEM, EDS-TEM, and HRTEM were used to characterize the size, crystal structure, texture, and chemical composition of the synthesis products. [ABSTRACT FROM AUTHOR]

The dissociation barriers of O and the adsorption energies of atomic O on the icosahedron M@Pd12, double icosahedron M2@Pd17 core-shell nanoclusters, and the M@Pd (M = Mn, Fe, Co, Ni, Cu, Pd) nanowires (NWs) are studied. It is found that the M@Pd NWs can probably serve as good catalysts for oxygen reduction reaction with both small O dissociation energy (0.10-0.23 eV) and O adsorption energy (1.19-1.28 eV). The reasons for the advantage of the M@Pd NWs are discussed in detail. [ABSTRACT FROM AUTHOR]

We report an efficient room-temperature synthesis of Au nanoparticles (NPs) using carbon dots (C-dots) as mediator in poly(ethylene glycol). The synthesis does not require any irradiation or heating for the reduction of the metal precursor and it yields smaller sized particles of ~15 nm, mostly octahedron in shape. The effect of varying concentrations of the Au precursor and C-dots on the synthesis was studied, which demonstrated the variation in particle size and shape with change in either the precursor or C-dots concentration. Time-resolved absorbance study for the synthesis of Au NPs showed the sigmoidal behavior for the autocatalytic growth having the lagging phase of induction period. The optimum concentration of the precursor and the C-dots were determined for the synthesis of well-dispersed Au NPs. The stability of the prepared Au NPs was also determined, showing that at optimum concentration of the precursor and C-dots, the particles were stable and did not precipitate for several days. [ABSTRACT FROM AUTHOR]

Ag-TiO nanocomposites were successfully developed from colloidal suspensions containing 750 or 1,500 ppm silver nanoparticles (AgNPs) deposited on 5 % (w/v) titanium dioxide nanoparticles (TiONPs) by a chemical reduction approach. The nanocomposites were characterized by diffuse reflectance UV-Vis spectroscopy (DRS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) and dynamic light scattering (DLS). DRS spectra showed an absorption band in visible region with maximum absorbance peaks at 452 and 444 nm attributed to AgNPs plasmon peaks, indicating the formation of small spherical or quasi-spherical Ag nanocrystals in nanocomposites. TEM and SEM analysis proved a nearly spherical morphology of particles (15-30 ± 5 nm average size in diameter). EDX analysis revealed the presence of Ti, O, and Ag in both nanocomposite powders having 1.37 or 2.34 wt% Ag content. DLS analysis yielded a bimodal particle size distribution in a narrow range (31.3 ± 0.5 or 23.4 ± 0.4 nm average particle diameter) and a good polydispersity (0.247 or 0.293 polydispersity index). The nanocomposites were screened for their in vitro antimicrobial activity against Gram-positive ( Bacillus subtilis and Staphylococcus aureus) and Gram-negative ( Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) bacterial and fungal ( Candida albicans) reference and clinical strains, in planktonic and adherent state, by qualitative and quantitative assays. The antibacterial activity increased with the increasing AgNPs content, being more intensive for Gram-positive bacteria. Both Ag-TiO nanocomposites exhibited a high antibiofilm activity. The obtained results recommend the use of the developed nanocomposites as antimicrobial and antibiofilm agents in practical applications without UV irradiation. The most effective agent proved to be the one with 2.34 wt% AgNPs content. [ABSTRACT FROM AUTHOR]

The present communication reports on a facile one-step solvothermal synthesis of highly crystallized MoS 2/TiO 2 nanocomposites for the first time. The TEM image shows the generation of a large amount of TiO 2 nanoparticles with diameters in the range of 5–8 nm. The photocurrent measurement suggests that loading a certain amount of MoS 2 can effectively improve separation of photogenerated carries. Cyclic voltammograms measurements reveal that TiO 2 modified with 1.0 wt% MoS 2 can reduce hydrogen reduction overpotential, thereby leading to enhanced photocatalytic activity. Photocatalytic H 2 evolution test suggests that 1.0 wt% MoS 2/TiO 2 nanocomposites show superior photocatalytic activity, and the H 2 production rate achieves 119.5 μmol h −1 g −1 and is about 19 times higher than that of TiO 2 alone, which could be attributed to the short diffusion distance in TiO 2 nanoparticles, efficient interfacial electron transfer from TiO 2 nanoparticles to MoS 2 surface, and reduced hydrogen reduction overpotential. Furthermore, the MoS 2/TiO 2 photocatalysts are stabile during the photocatalytic H 2 evolution test. Graphical abstract: [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]

A silver particle suspension obtained by a chemical reduction was used in this work. Monolayers of these particles (average size 28 nm) on mica modified by poly(allylamine hydrochloride) were produced under diffusion-controlled transport. Monolayer coverages, quantitatively determined by atomic force microscopy (AFM) and SEM, was regulated by adjusting the nanoparticle deposition time and the suspension concentration. The zeta potential of the monolayers was determined by streaming potential measurements carried out under in situ (wet) conditions. These measurements performed for various ionic strengths and pH were interpreted in terms of the three-dimensional (3D) electrokinetic model. The stability of silver monolayers was also investigated using streaming potential and the AFM methods. The decrease in the surface coverage of particles as a function of time and ionic strength varied between 10 −1 and 10 −4 M was investigated. This allowed one to determine the equilibrium adsorption constant Ka and the binding energy of silver particles (energy minima depth). Energy minima depth were calculated that varied between −18 kT for I = 10 −1 M and −19 kT for I = 10 −4 for pH 5.5 and T = 298 K. Our investigations suggest that the interactions between surface and nanoparticles are controlled by the electrostatic interactions among ion pairs. It was also shown that the in situ electrokinetic measurements are in accordance with those obtained by more tedious ex situ AFM measurements. This confirmed the utility of the streaming potential method for direct kinetic studies of nanoparticle deposition/release processes. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A method for synthesis of radiolabelled silver nanoparticles is reported. The method is based on proton activation of silver metal powder, enriched in 107Ag, with a 30.7 MeV proton beam. At this proton energy 105gAg is efficiently created, mainly via the 107Ag(p,3n) 105Cd →  105gAg reaction. 105gAg has a half-life of 41.29 days and emits easily detectable gamma radiation on decay to 105Pd. This makes it very useful as a tracing radionuclide for experiments over several weeks or months. Following activation and a period to allow short-lived radionuclides to decay, the powder was dissolved in concentrated nitric acid in order to form silver nitrate (AgNO 3), which was used to synthesise radiolabelled silver nanoparticles via the process of sodium borohydride reduction. For comparison, non-radioactive silver nanoparticles were synthesised using commercially supplied AgNO 3 in order to check if the use of irradiated Ag powder as a starting material would alter in any way the final nanoparticle characteristics. Both nanoparticle types were characterised using dynamic light scattering, zeta-potential and X-ray diffraction measurements, while additionally the non-radioactive samples were analysed by transmission electron microscopy and UV–Vis spectrometry. A hydrodynamic diameter of about 16 nm was determined for both radiolabelled and non-radioactive nanoparticles, while the electron microscopy on the non-radioactive samples indicated that the physical size of the metal NPs was (7.3 ± 1.4) nm. [ABSTRACT FROM AUTHOR]

Multidentate, thiolated, tryptophan-containing peptide conjugates were synthesized for the preparation of gold nanoclusters (AuNCs). Precursor Au 11(PPh 3) 8Cl 3 was prepared by the reduction of HAuCl 4, followed by the use of tryptophan-containing peptide conjugates in ligand displacement reactions, to afford near-infrared fluorescent AuNCs. The emission maxima for these newly synthesized AuNCs were ~715 nm. AuNCs were characterized with the help of UV–Vis, FTIR, fluorescence and MALDI analysis. FTIR spectra showed that the ligands bind to Au atoms through Au–S bonds, while MALDI mass spectra revealed that the clusters consisted of 20–23 Au atoms. Introduction of hydrophilic –COOH groups engendered water solubility to these AuNCs, enabling bioimaging applications. We demonstrate fluorescence imaging of the nematode C. elegans and confirm distribution of these AuNCs in nematode gut with the help of green fluorescent protein co-localization experiments. [ABSTRACT FROM AUTHOR]

A simple co-precipitation reaction between Ln 3+ cations (Ln = lanthanide) and phosphate ions in the presence of polyethylene glycol (PEG), including post-treatment under hydrothermal conditions, leads to the formation of Tb 3+-doped LaPO 4 crystalline nanorods. The nanoparticles obtained can be successfully coated with amorphous and porous silica, forming core/shell-type nanorods. Both products reveal intensive green luminescence under UV lamp irradiation. The surface of the core/shell-type product can also be modified with –NH 2 groups via silylation procedure, using 3-aminopropyltriethoxysilane as a modifier. Powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy confirm the desired structure and needle-like shape of the products synthesized. Fourier transform infrared spectroscopy and specific surface area measurements by Brunauer–Emmett–Teller method reveal a successful surface modification with amine groups of the core/shell-type nanoparticles prepared. The nanomaterials synthesized exhibit green luminescence characteristic of Tb 3+ ions, as solid powders and aqueous colloids, examined by spectrofluorometry. The in vitro cytotoxicity studies reveal different degree toxicity of the products. LaPO 4:Tb 3+@SiO 2@NH 2 exhibits the smallest toxicity against B16F0 mouse melanoma cancer cells and human skin microvascular endothelial cell lines, in contrast to the most toxic LaPO 4:Tb 3+@SiO 2. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this contribution, novel chitosan-stabilized gold nanoparticles (AuNPs) were prepared by mixing chitosan with citrate-reductive AuNPs under appropriate conditions. The as-prepared chitosan-stabilized AuNPs were positively charged and highly stably dispersed in aqueous solution. They exhibited weak resonance light scattering (RLS) intensity and a wine red color. In addition, the chitosan-stabilized AuNPs were successfully utilized as novel sensitive probes for the detection of heparin for the first time. It was found that the addition of heparin induced a strong increase of RLS intensity for AuNPs and the color change from red to blue. The increase in RLS intensity and the color change of chitosan-stabilized AuNPs caused by heparin allowed the sensitive detection of heparin in the range of 0.2-60 μM (~6.7 U/mL). The detection limit for heparin is 0.8 μM at a signal-to-noise ratio of 3. The present sensor for heparin detection possessed a low detection limit and wide linear range. Additionally, the proposed method was also applied to the detection of heparin in biological media with satisfactory results. [ABSTRACT FROM AUTHOR]

The present investigation reports a novel Ni-Ti-based NiCuCoTiTa alloy, obtained by arc melting cum suction casting route under ultrahigh-purity Ar atmosphere. X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy (TEM) investigations reveal a microstructure consisting of nanostructured eutectic between cubic NiTi and hexagonal NiTi with micron-scale NiTi and cubic TiNi dendrites. Detailed TEM investigation indicates substantial reduction in the interlamellar spacing as the alloy chemistry changes from binary to quinary. The alloy shows a high compressive strength, 2 GPa, with high plasticity 13 %. Fractography surface of this new alloy reveals mixed mode of fracture. The results are discussed in light of the available literature on deformation of nanostructured eutectic with micron-sized dendrites in the microstructures. [ABSTRACT FROM AUTHOR]

Green reduction of graphene oxide (GO) was performed using ascorbic acid (AA) in the presence of poly(sodium 4-styrenesulfonate), which resulted in reduced graphene oxide (PSS-rGO) with excellent solubility and stability in water. Large rGO sheets of 4 μm area and 1.1-nm thickness were obtained. The measurements showed that noncovalent functionalization with PSS molecules prevented rGO from aggregation. The parameters of graphite oxidation process and AA:GO w/w ratio were evaluated, and the obtained results showed that the properties of the reduced material (PSS-rGO) can be tailored by proper selection and adjustment of these parameters. [ABSTRACT FROM AUTHOR]

Silver (Ag) and copper (Cu) nanoparticles have shown great potential in variety applications due to their excellent electrical and thermal properties resulting high demand in the market. Decreasing in size to nanometer scale has shown distinct improvement in these inherent properties due to larger surface-to-volume ratio. Ag and Cu nanoparticles are also shown higher surface reactivity, and therefore being used to improve interfacial and catalytic process. Their melting points have also dramatically decreased compared with bulk and thus can be processed at relatively low temperature. Besides, regularly alloying Ag into Cu to create Ag-Cu alloy nanoparticles could be used to improve fast oxidizing property of Cu nanoparticles. There are varieties methods have been reported on the synthesis of Ag, Cu, and Ag-Cu alloy nanoparticles. This review aims to cover chemical reduction means for synthesis of those nanoparticles. Advances of this technique utilizing different reagents namely metal salt precursors, reducing agents, and stabilizers, as well as their effects on respective nanoparticles have been systematically reviewed. Other parameters such as pH and temperature that have been considered as an important factor influencing the quality of those nanoparticles have also been reviewed thoroughly. [ABSTRACT FROM AUTHOR]

The Cr(VI) pollutants are known to cause serious harm to the environment and human health. Chemical reduction is one of the efficient methods to eliminate the Cr(VI) pollutants. We synthesized polyvinylpyrrolidone-stabilized palladium (PVP-Pd) colloidal nanoparticles to catalytically reduce Cr(VI). The PVP-Pd colloidal nanocatalysts were active on the complete reduction of Cr(VI) to Cr(III) with a rate of 22.2 mol/(mol min) or a turn-over frequency (TOF) of 1,329 h at pH 4.0 and 45 °C. Magnetic FeO support was used for recycling the palladium nanocatalysts. The as-prepared Pd-FeO catalyst was easy to be separated from the reaction system by simply applying an external magnet and it exhibited efficient and stable reduction performance even after eight recycles. [ABSTRACT FROM AUTHOR]

In this report we present a simple, low-temperature method which is compatible with standard technology, to achieve graphene-based devices in large quantity. In this approach we take advantage of photocatalytic behavior of TiO to achieve photocatalytic reduction of chemically synthesized graphene oxide (GO) sheets. TiO nanoparticles have been deposited on GO sheets hanging from Au/SiO/Si interdigital electrodes to realize TiO/GO heterostructures. We investigated photocatalytic activity of TiO nanoparticles in the presence of UV-illumination, to reduce the GO sheets. Based on the Raman spectroscopy, the photocatalytic activity of TiO nanoparticles resulted in a decrease in the number of C-O bonds. Electrical measurements show that graphene sheets with the controlled electrical conductivity were obtained, so that higher illumination time led to higher conductivity and better reduction of GO sheets. Also, strain-induced photocatalytic reduction of the GO sheets has been investigated by their electrical characteristics. It has been shown for the first time that the electromechanical-induced strain enhances the photocatalytic behavior of the fabricated TiO/GO heterostructure significantly. [ABSTRACT FROM AUTHOR]

A monodisperse silver particle suspension was produced by a chemical reduction method in an aqueous medium using sodium citrate. The average particle size determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) was 28.5 nm. The DLS measurements confirmed that the suspension was stable for the ionic strength up to 3 × 10 M NaCl. The electrophoretic mobility measurements revealed that the electrokinetic charge of particles was negative for pH range 3-10, assuming −50 e for pH = 9 and 0.01 M NaCl. Using the suspension, silver particle monolayers on mica modified by poly(allylamine hydrochloride) were produced under diffusion-controlled transport. Monolayer coverage, quantitatively determined by AFM and SEM, was regulated within broad limits by adjusting the nanoparticle deposition time. This allowed one to uniquely express the zeta potential of silver monolayers, determined by the in situ streaming potential measurements, in terms of particle coverage. Such dependencies obtained for various ionic strengths and pH, were successfully interpreted in terms of the 3D electrokinetic model. A universal calibrating graph was produced in this way, enabling one to determine silver monolayer coverage from the measured value of the streaming potential. Our experimental data prove that it is feasible to produce uniform and stable silver particle monolayers of well-controlled coverage and defined electrokinetic properties. [ABSTRACT FROM AUTHOR]

Bioreduction of metal ions for the synthesis of nanoparticles of well-defined shape and size has been a great challenge in the field of nanotechnology. In this study, we explored the reduction potential of banana stem powder (BSP) for the synthesis of gold nanoparticles (GNP). The kinetics of GNP synthesis was monitored using UV-Vis spectroscopy. The synthesized GNP was characterized using dynamic light scattering (DLS), transmission electron microscopy, and fourier transform infrared spectroscopy. In addition, the cytotoxic potential of the synthesized GNP was investigated using human breast cancer (MCF-7) and normal human embryonic kidney (HEK-293) cell lines, as evaluated by changes in cell morphology, cell viability (MTT), and metabolic activity. BSP exhibited a strong reduction of Au(III) to Au (0) at room temperature within 5 min of reaction time. The synthesized GNP was found to be spherical with an average diameter of 30 nm by DLS analysis. The cytotoxicity analysis reveals a direct dose-response relationship, indicating that the cytotoxicity increases with increasing concentrations of the GNP. Significant cytotoxicity was observed in cancer cells (MCF-7) compared to normal cells (HEK-293). Also the cellular uptake of GNP was more pronounced in MCF-7 cells than HEK-293 cells as evidenced by zeta potential, implicating the possible reason for differential cytotoxicity. Thus the present study demonstrates the importance of these unique, less time-consuming, and stable BSP-mediated GNP as potential drug delivery vehicles in the application of anticancer therapy. [ABSTRACT FROM AUTHOR]

Modification of supported Pt catalyst by transition metal is effective for improving catalytic performance in fuel processing and electrochemical processes. In order to identify the role of CuO in Pt-Cu bimetallic nanoparticle catalyst in CO preferential oxidation in H-rich gas, three γ-FeO-supported Pt-Cu catalyst samples consisting of Pt-Cu alloy with different CuO content were synthesized by a radiolytic process. By managing the concentrations of the copper source and oxygen dissolved in the precursor solution, the CuO content was successfully varied by an order of magnitude without changing the structure and composition of the Pt-Cu alloy. In the catalytic tests, CuO-promoted CO oxidation significantly at around 100 °C. The catalyst with the highest CuO content showed the highest CO and O conversions. It was considered that the CuO phase promotes oxygen supply to CO chemisorbed on the Pt-Cu alloy surface. The alloy-CuO contact was suggested to be critical for the promoting effect. [ABSTRACT FROM AUTHOR]

Silicon nanoparticles (SiNPs) can be synthesized by a variety of methods. In many cases these routines are non-scalable with low product yields or employ toxic reagents. One way to overcome these drawbacks is to use one-pot synthesis based on the chemical reduction of micelles. In the following study trichloroalkylsilanes of differing chain lengths were used as a surfactant, and the level of capping, surface bonding and size of the nanoparticles formed has been investigated. FTIR results show that the degree of alkyl capping for SiNPs with different capping layers was constant, although SiNPs bound with shorter chains display a much higher level of Si-O owing to the reaction of the ethanol used in the method with uncapped sites on the particle. SiNPs with longer chain length capping show a sharp Si-H peak on the FTIR, these were heated at reflux with the corresponding 1-alkene to fully cap these particles, resulting in a reduction/disappearance of this peak with a minimal change in the intensity of the Si-O peak. Other techniques used to analyze the surface bonding and composition, XPS, H-NMR, and TEM/EDX, show that alkyl-capped SiNPs have been produced using this method. The optical properties showed no significant changes between the different capped SiNPs. [ABSTRACT FROM AUTHOR]

Non-spherical CdSe quantum dots were synthesized through high temperature reduction of cadmium and selenium in the presence of TOP (tri- n-octylphosphine) and TOPO (tri- n-octylphosphine oxide). The high affinity of phosphine oxide to the surface of CdSe nanocrystals typically leads to the formation of spherical particles with diameters between 1.5 and 10 nm. However, with lower temperatures and longer reaction times relative to conventional synthesis techniques, the formation of non-spherical nanocrystals dominated. The three reaction temperatures that were studied were 230, 250, and 270 °C. Results verify the need to quench CdSe nanocrystals immediately following the injection of selenium dissolved in TOP (TOPSe) if spherical particles are the desired shape. Nanocrystal shape evolves from sphere to rectangle to hexagon or triangle as the reaction time is extended regardless of temperature. The highest yield of rectangular particles (~89 %) was achieved while maintaining a temperature of 250 °C for 20 min. [ABSTRACT FROM AUTHOR]

In this paper, graphite oxide (GO) platelets functionalized by poly(ionic liquid) brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). The chemical reduction of these functionalized platelets was also investigated. The functionalized platelets and their reduced products were characterized and confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, ζ potential measurements, four-probe electrical measurements, and high-resolution transmission electron microscopy. Results demonstrated that the poly(ionic liquid) brushes could be grafted from the GO surface by SI-ATRP. The surface charges of the GO platelets surface transformed from negative to positive. Upon reduction by hydrazine, the functionalized platelets were partially reduced, as suggested by the observation that reduced GO exhibits electrical conductivity three magnitudes higher than that of original GO. Although partially reduced GO platelets were not as conductive as reduced GO without functionalization, they can be homogenously dispersed in water due to the presence of poly(ionic liquids) brushes. [ABSTRACT FROM AUTHOR]

Cellular uptake, cytotoxicity, and mechanisms of cytotoxicity of the positively charged Au nanoparticles (NPs) were examined in A549 cells, which are one of the most characterized pulmonary cellular systems. Positively charged Au NPs were prepared by chemical reduction using chitosan. The dimension and surface charge of Au NPs were examined by transmission electron microscopy (TEM), dynamic light scattering, and zeta potential measurements. The uptake of Au NPs into A549 cells was also monitored using TEM and dark-field microscopy (DFM) and z-stack confocal microRaman spectroscopy. DFM live cell imaging was also performed to monitor the entry of chitosan Au NPs in real time. The cytotoxic assay, using both methylthiazol tetrazolium and lactate dehydrogenase assays revealed that positively charged Au NPs decreased cell viability. Flow cytometry, DNA fragmentation, real-time PCR, and western blot analysis suggest that positively charged chitosan Au NPs provoke cell damage through both apoptotic and necrotic pathways. [ABSTRACT FROM AUTHOR]

Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8. [ABSTRACT FROM AUTHOR]

A colorimetric assay based on silver nanoparticles (NAC-Ag NPs) capped with N-acetyl- l-cysteine (CHNOS, NAC) has been developed which exhibits highly selectivity towards Ni over other cations such as Al, Cr, Fe, Co, Pb, Ba, Cd, Fe, Cu, Hg, Zn, Mn, Ag, Mg, Ca, Na, and K under specified conditions. Silver nanoparticles were prepared by reducing AgNO with sodium borohydride (NaBH) in the presence of NAC. The infrared spectra suggested that NAC was successfully capped on the surface of the silver nanoparticles. In the presence of Ni, rapid aggregation of NAC-Ag NPs was induced along with color change from yellow to deep orange. The absorbance ratio ( A/ A) was linear with the concentration of Ni in the wide range from 2 to 48 μM with a detection limit of 0.23 μM. The proposed method was applied successfully to the determination of Ni in tap water samples, and the recoveries were from 92 to 106 %. [ABSTRACT FROM AUTHOR]

We have previously reported that the silane coating of magnetic nanoparticles (MNPs) of maghemite phase could be used to protect iron oxide cores during plasma heat treatment, and even help to reduce their phase to magnetite with higher magnetization. In this work, an additional layer of an electrically conductive polypyrrole was added on top of the silane-coated MNPs, producing core-shell particles with sizes ranging from 150 to 500 nm. A microwave plasma heat treatment was used to convert the amorphous, already-conductive polypyrrole coatings into a more electrically conductive graphitic structure, while simultaneously reducing the iron oxide phase to magnetite. The treatment produced core-shell particles with better microwave absorption properties over the frequency of 1-18 GHz, with a maximum reflection loss (absorption) of these MNPs at −37 dB at 10.3 GHz for samples containing 70 wt% of plasma-treated core-shell nanoparticles embedded in wax. By comparison, the maximum absorption for the same amount of untreated nanoparticles was only −18 dB at 7.5 GHz. The improved electromagnetic wave absorption properties were due to higher electrical conductivity of the more ordered, graphitic-like polypyrrole shell structures. This relatively simple protocol could thus be used to synthesize highly magnetic and conductive nanocomposites for electromagnetic interference shielding applications, particularly at the high frequency range. [ABSTRACT FROM AUTHOR]

Inorganic or organic solid supported metal nanostructures have been attracted intensive interests in recent years. In this study, a novel and versatile approach for the preparation of solid supported silver nanocomposites is presented for the first time. In this method, the modified aldehyde groups on solid supporters are employed to reduce Ag[(NH)] ions. The in situ reduced silver nucleus are directly coated on the surfaces of the supports and then used as both seeds and catalysts for the self-catalytic growth of Ag NPs. In this reaction, no additional reduction and protective agents are needed. Moreover, the size of the Ag NPs can be tuned by varying the concentration of the Ag[(NH)] ions and the reaction time, which leads to the interesting change of the localized surface plasmon resonance absorption of the NPs. Such a synthesis method may realize the separation of nucleation and growth stages for the formation of Ag NPs and is proved to be a versatile method for the preparation of solid supported Ag nanocomposites (PS-Ag, FeO-Ag, and SiO-Ag), which would benefit the preparations and further applications of functional materials in near future. [ABSTRACT FROM AUTHOR]

The synthesis of silver nanoparticles has been carried out in aqueous solutions in a stirred semibatch reactor through the reduction of silver ions (Ag) by sulfite ions (SO), which were added at a tightly controlled rate up to a final sulfite/silver molar ratio of 0.45. Sodium dodecyl sulfate (SDS) was used as the stabilizer at concentrations below its critical micelle concentration. The effects of temperature, sulfite addition rate, and SDS concentration have been assessed. Ag turned to Ag in 5 min or less only when the synthesis was performed at 97 °C and not below. The sulfite addition rates studied were 0.5, 7.5, 15, and 90 μmol/min. The size, shape, polydispersity, and stability of the nanoparticles were determined by the sulfite addition rate and SDS concentration. At low SDS concentration (4 mM), stable, spherical shape, small size nanoparticles were formed only at the two intermediate sulfite addition rates. At the highest sulfite addition rate, 9 nm mean size spherical nanoparticles having a low ±5 nm polydispersity were produced at a high SDS concentration of 10 mM. With the low SDS concentration, larger truncated and spherical shape nanoparticles were obtained. UV-Vis spectrophotometry and transmission electron microscopy were used to characterize the nanoparticles. [ABSTRACT FROM AUTHOR]

Copper nanoparticles are prepared and size characterized using FESEM and HRTEM. Poly ethylene glycol (PEG), carboxy methyl cellulose (CMC) and poly N vinyl pyrrolidone (PVP) are used as the nanoparticle stabilizers. The reduction reactions of fourteen differently aromatic ring substituted nitro benzenes are carried out with NaBH solution catalyzed by the copper nanoparticles with PEG, CMC and PVP as stabilizers. Using time variance UV absorbance spectra, the progress of the reactions are kinetically monitored, the parameters such as product % yield, time of reaction and rate coefficient values are determined and used for deducing the comparative catalytic efficiency. The copper nanoparticles as synthesized using biopolymers such as PEG and CMC produce better reaction parameters than the PVP stabilized Cu nps. Also the effect of substituents in the aromatic ring of the nitro compounds reveals that −I substituents containing nitro compounds are better catalyzed than the +I substituents. The sizes of the three Cu nps are found to be 6, 12 and 15 nm corresponding to PEG, CMC and PVP stabilizers respectively. [ABSTRACT FROM AUTHOR]

Silver (Ag) nanoparticles with the crystallite size ranging from 13-24 nm were successfully doped onto the surface of iron oxide-silica coreshell particles. In the process, iron oxide particles having a size distribution within 8-19 nm were prepared by using a reverse co-precipitation method followed by the formation of iron oxide-core with silica shell (with 50-150 nm diameter of silica spheres) by using a modified Stöber method. The reduction of Ag ions was done at room temperature in a solution containing polyvinylpyrrolidone and ethanol by using mechanical and ultrasonic mixing. Four different synthesis approaches were used in doping of Ag nanoparticles. The phase, morphology, optical and magnetic properties of the synthesized powders were characterized by using X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope, UV-visible spectrometer (UV-Vis) and vibrating sample magnetometer. Spherical morphology of the Ag nanoparticles was found to deposit on the iron oxide-silica surfaces. The particle size distribution is depending on the synthesis approach used. The UV-Vis absorption peak at 404-410 nm of wavelength confirmed the existence of the Ag nanoparticles. [ABSTRACT FROM AUTHOR]

The adsorption behavior of mesoporous iron nanocomposites was investigated with respect to chromate [Cr(VI)] removal from aqueous solutions to consider its application for purifying chromate-contaminated wastewaters. These nanocomposites were prepared by borohydride reduction in aqueous solutions containing varying concentrations of acetone as co-solvent. Using batch methods, enhanced adsorption of Cr(VI) on the nanocomposite surface was achieved at neutral pH conditions, which subsequently resulted in Cr(VI) reduction to Cr(III). The Langmuir model was found to excellently describe the adsorption process, offering a maximum adsorptive capacity of 34.1 mg/g for composites prepared with 50 % acetone concentration. The Cr(VI) removal efficiency of these iron nanocomposites is strongly dependent on the acetone concentration, as evident from their (1) increased surface area (141.1 m/g) compared to conventional iron nanoparticles (33.2 m/g), and (2) highly porous and acicular structure, which efficiently traps Cr(VI) through adsorption. X-ray photoelectron spectroscopy analysis of Cr(III) on the nanocomposite surface confirmed that Cr(VI) removal from solution was achieved by sequential adsorption-reduction. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles were prepared by a reduction-precipitation method and coated with an amino silane coupling agent. Guanine (Gua) was conjugated to the magnetic nanoparticles (MNPs) using glutaraldehyde as a cross-linker. Common techniques (Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and vibrating electron microscopy) were used to assess the properties of the particles. Structural investigations showed that amino silane-coated MNPs had a particle size of about 40-60 nm in diameter with a spherical morphology. The guanine-conjugated MNPs were radiolabeled with Tc(I)-tricarbonyl core (Tc(CO)-MNP-Gua) with a labeling yield of 72 ± 4 %. Pure radiolabeled magnetic particles were obtained by washing them with saline solution, and the radiochemical purity of Tc(CO)-MNP-Gua was 98 ± 2 % in the final solution. The biologic distribution of guanine MNPs was assessed in New Zealand rabbits using a gamma camera. In the in vivo experiment, a high level of radioactivity was observed in the lungs and liver soon after intravenous administration of Tc(CO)-MNP-Gua. [ABSTRACT FROM AUTHOR]

In this study, an environmental friendly process for the synthesis of silver nanoparticles (AgNPs) using a fungus Aspergillus tamarii has been investigated. The process of silver ion reduction by the fungal extracellular filtrate was spontaneous which lead to the development of an easy process for synthesis of silver nanoparticles. The AgNPs formed were characterized using UV-Visible spectrum, FTIR, and SEM. The results revealed that silver ions reduction by the fungal extracellular filtrate started at 420 nm after 0.5 h of incubation time. The FTIR peaks were observed at 1393, 1820, 2727, and 3545 cm. The SEM result showed the distribution of spherical AgNPs ranging from 25 to 50 nm. [ABSTRACT FROM AUTHOR]

We report on the observation of the development of superconductivity through interparticle interactions in 3, 5, 7, and 23 nm ferrimagnetic-like Sn nanoparticle assemblies. The Sn nanoparticles are fabricated using the gas condensation method. Each sample consists of a macroscopic amount of individual Sn nanoparticles without a capping molecule. Ferrimagnetism is found but no sign of superconductivity can be detected when the 3 nm particles are very loosely assembled. A reduction in the mean particle moment results when the packing fraction of the assembly is increased. Superconductivity occurs when a critical packing fraction is reached. Beyond this, the superconducting transition temperature T continues to increase and noticeably exceeds that of the bulk T. The enhancement of superconductivity by interparticle interactions has also been observed in 5, 7, and 23 nm particle assemblies, with the effect becoming less significant in larger particles. We attribute these observations to the transfer of electrons between the surface and the core regions of the nanoparticles triggered by finite size effects and interparticle interactions. [ABSTRACT FROM AUTHOR]

The continuous synthesis of nickel nanoparticles (NiNPs) in a static microchannel T-mixer by the reduction of NiCl·6HO in the presence of ethylene glycol without a stabilizing/capping agent was investigated. The nanoparticles were formed in accordance with the modified polyol process with hydrazine used as a reducing agent and NaOH as a catalyst for nanoparticle formation. The reaction mechanism for NiNP formation was investigated in batch with the help of Fourier transform infrared spectroscopy and X-ray diffraction (XRD) techniques. Parameters were found for reducing reaction times from 60 to 1 min. The effects of temperature (60-120 °C) and NaOH concentration (0.1 and 0.5 M) on batch-processed particle characteristics were also studied using XRD, transmission electron microscope and electron microprobe analysis. Average particle size was reduced from 9.2 ± 2.9 to 5.4 ± 0.9 nm at higher temperature and NaOH concentration. Adaptation of this chemistry to a static microchannel T-mixer for continuous synthesis resulted in smooth, spherical particles. Increases in the reaction temperature from 120 to 130 °C resulted in a narrow size distribution of 5.3 ± 1 nm and also resulted in magnetic properties of 5.1 emu/g (saturation magnetization), 1.1 emu/g (remanent magnetization), and 62 Oe (coercivity). [ABSTRACT FROM AUTHOR]