Self-aligned and bundled electrospun fibers prepared from blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with a hairt-rod polyphenylene copolymer

Cataloged from PDF version of article.Bundled and self-aligned fibers were obtained by electrospinning blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with a hairy-rod polyphenylene-g-polystyrene/poly(a-caprolactone) (PP-g-PS/PCL) copolymer. The self-alignment and bundling characteristics of these electrospun fibers were ascribed to the unique molecular architecture of the conjugated polymer, PP-g-PS/PCL, and its interactions with the solvent and the polymer matrixes used for the electrospinning. The self-alignment and bundling was found to be much more pronounced for PP-g-PS/PCL-PS blend when compared to PP-g-PS/PCL-PMMA blend. Furthermore we found that the degree of self-alignment of the fiber bundles was enhanced by increasing the amount of PP-g-PS/PCL in the blends but the alignment completely disappeared when the solvent dimethylformamide was changed to chloroform. © 2009 Elsevier B.V. All rights reserved

Electrospun polyethylene oxide (PEO) nanofibers containing cyclodextrin inclusion complex

In this study, we obtained functional electrospun nanofibers containing stable fragrance/flavor molecule facilitated by cyclodextrin inclusion complexation. Menthol was used as a model fragrance/flavor molecule and we have electrospun poly(ethylene oxide) (PEO) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-IC). We used two different solvent systems; water and water:ethanol and three types of CDs; α-CD, β-CD and γ-CD in order to find the optimal performance for the stabilization of menthol at high temperatures. We observed that the solvent system used for electrospinning process and the types of CDs (α-CD, β-CD and γ-CD) are very important to obtain CD-menthol-IC which ultimately determines the durability and temperature stability of menthol in the PEO nanofibrous web. We found out that it is better to use water rather than the water:ethanol solvent system for the inclusion complexation and additionally β-CD and γ-CD are most favorable choices since they are able to form complexation with menthol in the water solvent system. Despite the high volatility nature of menthol, our results demonstrated that the stability and temperature release of menthol was sustained to a very high and a broad temperature range (100 °C-250 °C) for PEO nanowebs containing CD-menthol-IC whereas the PEO nanofibers without CD and without CD-menthol complex could not preserve menthol even during storage. In brief, the results are very encouraging and open up for a variety of new exciting possibilities for the development of multi-functional electrospun nanofibers containing cyclodextrin inclusion complexes. Copyright © 2011 American Scientific Publishers All rights reserved

Palladium Nanocrystals on Al₂O₃: Structure and Adhesion Energy

We have investigated the structure and morphology of nanosized palladium clusters supported by a thin Al2O3 film on NiAl(110) using scanning tunneling microscopy. Well-ordered clusters with a diameter above ≈40Å were imaged with atomic resolution, allowing a crystallographic identification of the cluster facets. A new method to obtain quantitative information on the work of adhesion (adhesion energy) of metal clusters deposited on oxides is introduced. For Pd on Al2O3 we obtain a value of Wadh=2.8±0.2J/m2. This result is at variance with values recently derived on the basis of ab initio density-functional theory

Looking at electronic wave functions on metal surfaces

The project described here is not only a beautiful example of the visual side tophysics, it is also a beautiful example of international cooperation. The first use of the idea—to apply a Fourier transform to STM pictures to see electron waves instead of just the surface atoms—came out of a collaboration between Plummer, Sprunger and the Aarhus group headed by Besenbacher. Hofman, who had beenworking at Tennessee, took Be(1010) samples to Berlin where the images shown in this pictorial were taken. All of the participants are now preparing a paper on the use of a Fourier transform to map the Fermi contour at metal surfaces

Characterisation of internal morphologies in electrospun fibers by X-ray tomographic microscopy

Electrospun fabrics for use in, for example, tissue engineering, wound dressings, textiles, filters and membranes have attracted a lot of attention due to their morphological nanoscale architectures which enhance their physical properties. A thorough detailed internal morphological study has been performed on electrospun polystyrene (PS) fibers produced from dimethylformamide (DMF) solutions. Investigations by transmission electron microscopy (TEM) and thorough studies for the first time by synchrotron based X-ray tomographic microscopy (XTM) revealed that the individual electrospun PS fibers and beads have a graded density and in some cases even an internal porous structure. © The Royal Society of Chemistry 2011

Size-Dependent Dissociation of Carbon Monoxide on Cobalt Nanoparticles

[[abstract]]In situ soft X-ray absorption spectroscopy (XAS) was employed to study the adsorption and dissociation of carbon monoxide molecules on cobalt nanoparticles with sizes ranging from 4 to 15 nm. The majority of CO molecules adsorb molecularly on the surface of the nanoparticles, but some undergo dissociative adsorption, leading to oxide species on the surface of the nanoparticles. We found that the tendency of CO to undergo dissociation depends critically on the size of the Co nanoparticles. Indeed, CO molecules dissociate much more efficiently on the larger nanoparticles (15 nm) than on the smaller particles (4 nm). We further observed a strong increase in the dissociation rate of adsorbed CO upon exposure to hydrogen, clearly demonstrating that the CO dissociation on cobalt nanoparticles is assisted by hydrogen. Our results suggest that the ability of cobalt nanoparticles to dissociate hydrogen is the main parameter determining the reactivity of cobalt nanoparticles in Fischer–Tropsch synthesis.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子