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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]

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]

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]

Au nanoparticles with diameters of ca . 15 nm were synthesized according to the well-developed citrate reduction method. It was found that the nanoparticles tended to attach and fuse into each other to form chain-like structures with the removal of the stabilizing agents. UV-Vis absorption and HRTEM characterizations provided solid evidence for the fused features. On the basis of the HRTEM observations, we believed the decreased surface energy as well as the dipole-dipole interaction is responsible for the formation of the chain-like structures. SERS activity investigation indicated that the intensities of the b2-type bands have close relation with the concentration of the probing molecules, which further confirmed the chemical effect character of the b2-type scatterings. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (Au NPs) in three different silica based sol-gel matrixes with and without surfactants are prepared. They are characterized by UV-vis absorbance and transmission electron microscopic (TEM) studies. The size and shape of Au NPs varied with the organo-functional group present in the sol-gel matrix. In the presence of mercaptopropyl functionalized organo-silica, large sized (200-280 nm) spherical Au NPs are formed whereas in the presence of aminopropyl functionalized organo-silica small sized (5-15 nm) Au NPs are formed inside the tube like organo-silica. Further, it is found that Au NPs act as efficient catalyst for the reduction of organic dyes. The catalytic rate constant is evaluated from the decrease in absorbance of the dye molecules. Presence of cationic or anionic surfactants greatly influences the catalytic reaction. The other factors like hydrophobicity of the organic dyes, complex formation of the dyes with anionic surfactants, repulsion between dyes and cationic surfactant, adsorption of dyes on the Au NPs also play important role on the reaction rate. [ABSTRACT FROM AUTHOR]

The authors have successfully synthesized Pd-on-Pt (thickness: 12 nm) and Au-on-Pt bimetallic nanosheaths on multiwalled carbon nanotubes (MWCNTs) via a seed-mediated growth approach. Pt nanoparticles as seeds were pre-deposited on MWCNTs with uniform distribution followed by the successive seed-mediated growth of metal atoms reduced by a weak reducing agent, ascorbic acid. The essential role of pre-deposited nanoseed particles on MWCNTs was demonstrated. The as-prepared materials were characterization by transition electron microscopy, energy-dispersive X-ray spectroscopy, and element mapping tools. The current strategy extends the classical seed-mediated growth method to prepare bimetallic nanosheath on MWCNT support. [ABSTRACT FROM AUTHOR]

With the aim of developing dimensionally stable-supported catalysts for direct methanol fuel cell application, Pt and Pt-Ru catalyst nanoparticles were deposited onto undoped and boron-doped diamond nanoparticles (BDDNPs) through a chemical reduction route using sodium borohydride as a reducing agent. As-received commercial diamond nanoparticles (DNPs) were purified by refluxing in aqueous nitric acid solution. Prompt gamma neutron activation analysis and transmission electron microscopy (TEM) techniques were employed to characterize the as-received and purified DNPs. The purified diamond nanoparticulates, as well as the supported Pt and Pt-Ru catalyst systems, were subjected to various physicochemical characterizations, such as scanning electron microscopy, energy dispersive analysis, TEM, X-ray diffraction, inductively coupled plasma-mass spectrometry, X-ray photoelectron spectroscopy, and infrared spectroscopy. Physicochemical characterization showed that the sizes of Pt and Pt-Ru particles were only a few nanometers (2-5 nm), and they were homogeneously dispersed on the diamond surface (5-10 nm). The chemical reduction method offers a simple route to prepare the well-dispersed Pt and Pt-Ru catalyst nanoparticulates on undoped and BDDNPs for their possible employment as an advanced electrode material in direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Abstract  Three cathode catalysts (60% Pt/C, 30% Pt/C and 60% Pt–Fe/C), with a particle size of about 2–3 nm, were prepared to investigate the effect of ethanol cross-over on cathode surfaces. All samples were studied in terms of structure and morphology by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Their electrocatalytic behavior in terms of oxygen reduction reaction (ORR) was investigated and compared using a rotating disk electrode (RDE). The tolerance of cathode catalysts in the presence of ethanol was evaluated. The Pt–Fe/C catalyst showed both higher ORR activity and tolerance to ethanol cross-over than Pt/C catalysts. Moreover, the more promising catalysts were tested in 5 cm2 DEFC single cells at 60 and 80 °C. An improvement in single cell performance was observed in the presence of the Pt–Fe catalyst, due to an enhancement in the oxygen reduction kinetics. The maximum power density was 53 mW cm−2 at 2 bar rel. cathode pressure and 80 °C. [ABSTRACT FROM AUTHOR]

Abstract  Gold nanoparticles were prepared by a simple heat-treated method using polyvinyl alcohol (PVA) as reducing and stabilizing agent in this article. UV/Vis spectroscopy was used to monitor the preparation. The formation of a sharp band at ~530 nm in the UV/Vis spectra and morphological characters revealed by transmission electron microscopy indicated the generation of Au nanoparticles. The PVA film embedded with Au nanoparticles was prepared by flow casting method and characterized by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. The results showed that Au nanoparticles embedded in PVA film can improve the thermal stability of the film under investigation, leading to interesting technological applications. [ABSTRACT FROM AUTHOR]

Abstract  Simple strategies for producing silver and gold nanoparticles (AgNP and AuNP) along with the corresponding core shell nanoparticles (Au–Ag and Ag–Au) by reduction of the metal salts AgBF4 and HAuCl4 by NaBH4 in water will be presented. The morphologies of the obtained nanoparticles are determined by the order of addition of reactants. The obtained NPs, with sizes in the range 3–40 nm, are characterized by transmission electronic microscopy (TEM) and UV–Vis absorption spectroscopy, so as to evaluate their qualities. Moreover, a direct electrochemical detection protocol based on a cyclic voltammetry in water solution that involves the use of glassy carbon electrode is also applied to characterize the prepared NPs. The developed NPs and the related electroanalytical method seem to be with interest for future sensing and biosensing applications including DNA sensors and immunosensors. [ABSTRACT FROM AUTHOR]