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Hollow Core (hollow + core)
Selected AbstractsSynthesis of Core,Shell Inorganic NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Ronen Kreizman Abstract New materials and techniques pertaining to the synthesis of inorganic nanotubes have been ever increasing since the initiation of the field in 1992. Recently, WS2 nanotubes, which are produced now in large amounts, were filled with molten lead iodide salt by a capillary wetting process, resulting in PbI2@WS2 core,shell nanotubes. This work features progress in the synthesis of new core,shell nanotubes, including BiI3@WS2 nanotubes produced in a similar same manner. In addition, two new techniques for obtaining core,shell nanotubes are presented. The first is via electron-beam irradiation, i.e., in situ synthesis within a transmission electron microscope. This synthesis results in SbI3 nanotubes, observed either in a hollow core of WS2 ones (SbI3@WS2 nanotubes), or atop of them (WS2@SbI3 nanotubes). The second technique involves a gaseous phase reaction, where the layered product employs WS2 nanotubes as nucleation sites. In this case, the MoS2 layers most often cover the WS2 nanotube, resulting in WS2@MoS2 core,shell nanotubes. Notably, superstructures of the form MoS2@WS2@MoS2 are occasionally obtained. Using a semi-empirical model, it is shown that the PbI2 nanotubes become stable within the core of MoS2 nanotubes only above a critical core diameter of the host (>12,nm); below this diameter the PbI2 crystallizes as nanowires. These model calculations are in agreement with the current experimental observations, providing further support to the growth mechanism of such core,shell nanotubes. [source] Aqueous Near-Infrared Fluorescent Composites Based on Apoferritin-Encapsulated PbS Quantum Dots,ADVANCED MATERIALS, Issue 19 2008Barbara Hennequin PbS nanocrystals entrapped in the hollow core of apoferritin protein cages are synthesized in aqueous solution by both reassembly and nanoreactor routes. In both cases, apoferritin limits the size of the PbS quantum dot it can encapsulate to 8 nm and provides a route to the creation of a stable near-infrared fluorescent composite. [source] Cagelike polymer microspheres with hollow core/porous shell structuresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007Xiaodong He Abstract Submicron-scaled cagelike polymer microspheres with hollow core/porous shell were synthesized by self-assembling of sulfonated polystyrene (PS) latex particles at monomer droplets interface. The swelling of the PS latex particles by the oil phase provided a driving force to develop the hollow core. The latex particles also served as porogen that would disengage automatically during polymerization. Influential factors that control the morphology of the microspheres, including the reserving time of emulsions, polymerization rate, and the Hildebrand solubility parameter and polarity of the oil phase, were studied. A variety of monomers were polymerized into microspheres with hollow core/porous shell structure and microspheres with different diameters and pore sizes were obtained. The polymer microspheres were characterized by scanning electron microscopy, transmission electron microscopy, optical microscopy, and Fourier transform infrared spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 933,941, 2007 [source] X-ray photoelectron spectroscopy and tribology studies of annealed fullerene-like WS2 nanoparticlesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008B. Späth Abstract The time dependent chemical changes occurring at the surface of inorganic fullerene-like (IF) nanoparticles of WS2 were investigated using X-ray photoelectron spectroscopy (XPS) and compared to those of bulk powder, 2H-WS2. It was possible to follow the long term surface oxidation and carbonization occurring at defects on the outermost surface (0001) molecular layers of the inorganic fullerene-like nanoparticles. Vacuum annealing was shown to remove most of these contaminants and bring the surface close to its pristine stoichiometric composition. In accordance with previous measurements, further evidence was obtained for the existence of water molecules, which were entrapped in the hollow core and interstitial defects of the fullerene-like nanoparticles during the synthesis. These water molecules were also shown to be removable by the vacuum annealing process. Chemically resolved electrical measurements (CREM) in the XPS showed that the IF samples had become less p-type after the vacuum annealing. Finally, tribological measurements showed that the vacuum annealed IF samples performed better as an oil additive than the non-annealed IF samples and the 2H-WS2 powder. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AFM study of the surface morphology of the {100} cleavage planes of L-arginine phosphate monohydrate single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2004Y. L. Geng Abstract Surface morphology of the {100} cleavage planes of L-arginine phosphate monohydrate single crystals grown from aqueous solutions is described and discussed. Different from the previous studies, dislocations are not frequently detected and most of them don't have hollow cores on the emergence points. Various step patterns are also described. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication and Drug Delivery of Ultrathin Mesoporous Bioactive Glass Hollow FibersADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Youliang Hong Abstract Ultrathin mesoporous bioactive glass hollow fibers (MBGHFs) fabricated using an electrospinning technique and combined with a phase-separation-induced agent, poly(ethylene oxide) (PEO), are described. The rapid solvent evaporation during electrospinning and the PEO-induced phase separation process demonstrated play vital roles in the formation of ultrathin bioactive glass fibers with hollow cores and mesoporous walls. Immersing the MBGHFs in simulated body fluid rapidly results in the development of a layer of enamel-like apatite mesocrystals at the fiber surfaces and apatite nanocrystals inside the hollow cores. Drug loading and release experiments indicate that the drug loading capacity and drug release behavior of the MBGHFs strongly depends on the fiber length. MBGHFs with fiber length >50,µm can become excellent carriers for drug delivery. The shortening of the fiber length reduces drug loading amounts and accelerates drug release. The MBGHFs reported here with sophisticated structure, high bioactivity, and good drug delivery capability can be a promising scaffold for hard tissue repair and wound healing when organized into 3D macroporous membranes. [source] | |||||||||||||