160,803 research outputs found
Asymmetric tungsten oxide nanobrushes via oriented attachment and Ostwald ripening
No full textTungsten oxide nanobrushes were synthesized using a solvothermal approach that lead to self-branching in the presence of citric acid and hexadecylamine as surfactants. Our synthetic approach yielded branched nanorods of tungsten oxide in a single synthetic step. Based on our results, we propose a phenomenological pathway for the formation, branching, and assembly of these tungsten oxide brushes. The formation of tungsten oxide brushes proceeds by thermal decomposition of ammonium tungstate in the presence of citric acid and hexadecylamine. The pale blue powder obtained after solvothermal reaction was analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The field emission (FE) properties of the tungsten oxide nanostructures which can be tailored by their aspect ratio and the hierarchical nanostructures follow a Fowler-Nordheim behavior. RI Tremel, Wolfgang/D-8125-2011; Mugnaioli, Enrico/E-6237-2011; Kolb, Ute/A-2642-2011; GOLBERG, Dmitri/H-2776-201
Synthesis of Fullerene- and Nanotube-Like SnS2 Nanoparticles and Sn/S/Carbon Nanocomposites
No full textSnS2 nested fullerene-type (IF) nanoparticles, nanotubes, and SnS2/C hybrid nanostructures were obtained by vapor transport starting from elemental tin and CS2. The reaction was carried out in a single-step process by heating elemental tin metal powder in a horizontal tube furnace at 800-1000 degrees C. TEM analysis allowed proposing a plausible mechanism for the formation of fullerene-like particles of SnS2 as well as tubes and scrolls from nanosheets of SnS2. Pure material could be obtained by optimizing the reaction based on a product analysis using powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) combined with energy-dispersive X-ray spectroscopy (EDX). RI Kolb, Ute/A-2642-2011; Tremel, Wolfgang/D-8125-2011; Mugnaioli, Enrico/E-6237-201
Interaction of Alkaline Metal Cations with Oxidic Surfaces: Effect on the Morphology of SnO2 Nanoparticles
No full textReaction pathways to SnO2 nanomaterials through the hydrolysis of hydrated tin tetrachloride precursors were investigated. The products were prepared solvothermally starting from hydrated tin tetrachloride and various (e.g., alkali) hydroxides. The influence of the precursor base on the final morphology of the nanomaterials was studied. X-ray powder diffraction (XRD) data indicated the formation of rutile-type SnO2. Transmission electron microscopy (TEM) studies revealed different morphologies that were formed with different precursor base cations. Data from molecular dynamics (MD) simulations provide theoretical evidence that the adsorption of the cations of the precursor base to the faces of the growing SnO2 nanocrystals is crucial for the morphology of the nanostructures. RI Birkel, Alexander/D-6123-2011; Tremel, Wolfgang/D-8125-2011; Mugnaioli, Enrico/E-6237-2011; Loges, Niklas/F-2479-201
Structure analysis of titanate nanorods by automated electron diffraction tomography
No full textA hitherto unknown phase of sodium titanate, NaTi3O6(OH)center dot 2H(2)O, was identified as the intermediate species in the synthesis of TiO2 nanorods. This new phase, prepared as nanorods, was investigated by electron diffraction, X-ray powder diffraction, thermogravimetric analysis and high-resolution transmission electron microscopy. The structure was determined ab initio using electron diffraction data collected by the recently developed automated diffraction tomography technique. NaTi3O6(OH)center dot 2H(2)O crystallizes in the monoclinic space group C2/m. Corrugated layers of corner- and edge-sharing distorted TiO6 octahedra are intercalated with Na+ and water of crystallization. The nanorods are typically affected by pervasive defects, such as mutual layer shifts, that produce diffraction streaks along c*. In addition, edge dislocations were observed in HRTEM images. RI Tremel, Wolfgang/D-8125-2011; Andrusenko, Iryna/E-6239-2011; Mugnaioli, Enrico/E-6237-2011; Kolb, Ute/A-2642-201
Synthesis of Hierarchically Grown ZnO@NT-WS2 Nanocomposites
No full textA chemically specific and facile method for growth of ZnO nanorods on WS2 nanotubes (NT-WS2) is reported. The modification strategy is based on the chalcophilic affinity of Zn, which serves as an anchor to immobilize ZnO colloids onto the WS2 nanotubes. The surface bound ZnO colloids have been used as a seed to grow ZnO nanorods on WS2 nanotubes. The immobilization of ZnO colloids was monitored by UV-vis spectroscopy and photoluminescence spectroscopy whereas the growth of ZnO nanorods was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RI Kolb, Ute/A-2642-2011; tahir, Muhammad Nawaz/B-7650-2011; Tremel, Wolfgang/D-8125-2011; Mugnaioli, Enrico/E-6237-201
Solution Synthesis of a New Thermoelectric Zn1-xSb Nanophase and Its Structure Determination Using Automated Electron Diffraction Tomography
No full textEngineering materials with specific physical properties have recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium- and long-wavelength phonons thereby lowering the thermal conductivity of the system. Low thermal conductivity is a prerequisite for effective thermoelectric materials, and the challenge is to limit the transport of heat by phonons, without simultaneously decreasing charge transport. A solution-phase technique was devised for synthesis of thermoelectric "Zn4Sb3" nanocrystals as a precursor for phase segregation into ZnSb and a new Zn-Sb intermetallic phase, Zn1+delta Sb, in a peritectoid reaction. Our approach uses activated metal nanoparticles as precursors for the synthesis of this intermetallic compound. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. Both phases were identified and structurally characterized by automated electron diffraction tomography combined with precession electron diffraction. An ab initio structure solution based on electron diffraction data revealed two different phases. The new pseudo-hexagonal phase, Zn1+delta Sb, was identified and classified within the structural diversity of the Zn-Sb phase diagram. RI Kolb, Ute/A-2642-2011; Birkel, Christina/D-6144-2011; Tremel, Wolfgang/D-8125-2011; Mugnaioli, Enrico/E-6237-201
Silicatein-mediated incorporation of titanium into spicules from the demosponge Suberites domuncula
No full textPrimmorphs (a three-dimensional sponge primary cell culture system) have been revealed to be a cell/tissue nano-factory for the production of tailor-made hybrid nanostructures. Growth of primmorphs is stimulated by the presence of a titanium alkoxide precursor tolerating titania (TiO(2)) concentrations up to 250 mu M. The presence and activity of silicatein in primmorphs has been analyzed by gel electrophoresis and Western blotting. Results of studies by scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy have revealed silica and titania to be co-localized on nanosized spicules. Our findings suggest that the incorporation of titania into the nanosized spicule is enzymatically mediated via active silicatein in an orchestrated mechanism. RI Kolb, Ute/A-2642-2011; tahir, Muhammad Nawaz/B-7650-2011; Natalio, Filipe/D-4417-2011; Tremel, Wolfgang/D-8125-2011; Mugnaioli, Enrico/E-6237-201
Mismatch Strain versus Dangling Bonds: Formation of "Coin-Roll Nanowires" by Stacking Nanosheets
No full text(Figure Presented) The third dimension comes to the rescue in the synthesis of laterally confined 2D crystals. Graphene-type sheets of layered metal(IV) chalcogenides are stabilized by stacking to form nano-objects that resemble a coin roll. Mismatch strain between NbS2 and WS2 lattices is important for the stabilization of the coin-roll structure as well as for preventing the formation of the intrinsically more stable scroll structures such as fullerenes or nanotubes. © 2010 Wiley-VCH Verlag GmbH &. Co. KGaA
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