Synthesis and properties of water soluble single‐walled carbon nanotube graft ionic polyacetylene nanocomposites

Water‐soluble single‐walled carbon nanotube‐polyacetylene [SWNT‐PA, SWNT‐P(2EPy‐MeTf)] nanocomposites have been synthesized by using the surface initiated “grafting‐from” method. The FT‐IR spectra confirmed the formation of an amide bond between the functionalized SWNTs and the initiator, 4‐(2‐Aminoethyl) pyridine, to polymerize N‐Methyl‐2‐ethynlypyridinium triflate (2EPy‐MeTf). UV‐vis spectroscopy indicated that the degree of polymerization of P(2EPy‐MeTf) in the SWNT‐polyacetylene composites is 15, based on the Lewis‐Calvin equation. The SWNT‐polyacetylene composites have been characterized by TGA, AFM, and TEM. From TGA analysis, the loading of SWNTs in the SWNT grafted ionic polyacetylenes is estimated to be 22%. AFM and TEM images clearly showed that the nanotube is wrapped with the PA. The SWNT‐polyacetylene composites displayed high water solubility (8 mg/ml). The room temperature electrical conductivity of the doped SWNT‐polyacetylene composites was found to be in the range of 10⁻³ to 10⁻⁴ S/cm, an order of magnitude of increase over neat P(2EPy‐MeTf) and a two order of magnitude increase over Dendrimer‐polyacetylen composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of reduction conditions on electrocatalytic activity of a ternary PtNiCr/C catalyst for methanol electro-oxidation

The effect of reduction conditions on a Pt₂₈Ni₃₆Cr₃₆/C catalyst was investigated by using two different reduction methods: hydrogen reduction and NaBH₄ reduction. In hydrogen reduced catalysts, dissolution of metallic Ni and Cr was observed during cyclic voltammetry (CV) tests, and a larger amount of Ni and Cr was dissolved when reduced at higher temperatures. For methanol electro-oxidation, the highest specific current density of 1.70 A m⁻² at 600 s of the chronoamperometry tests was observed in the catalyst reduced at 300 °C, which was ∼24 times that of a Pt/C catalyst (0.0685 A m⁻²). In NaBH₄ reduced catalysts, formation of an amorphous phase and a more Pt-rich surface was observed in X-ray diffraction and CV results, respectively, with increasing amounts of NaBH₄. When reduced by 50 times of the stoichiometric amount of NaBH₄, the PtNiCr/C catalyst (PtNiCr-50t) showed a current density of 34.1 A g_{noble metal}⁻¹, which was 81% higher than the 18.8 A g_{noble metal}⁻¹ value of a PtRu/C catalyst at 600 s of the chronoamperometry tests. After 13 h of chronoamperometry testing, the activity of the PtNiCr-50t (15.0 A g_{noble metal}⁻¹) was 110% higher than the PtRu/C catalyst (7.15 A g_{noble metal}⁻¹). The PtNiCr/C catalyst shows promise as a Ru-free methanol oxidation catalyst.     

Effect of number of walls on plasmon behavior in carbon nanotubes

We investigate the physical parameters controlling the low-energy screening in carbon nanotubes via electron energy loss spectroscopy and inelastic X-ray scattering. Two plasmon-like features are observed, one near 9 eV (the so-called π plasmon) and one near 20 eV (the so-called π + σ plasmon). At large nanotube diameters, the π + σ plasmon energies are found to depend on the number of walls and not on the radius or chiral vector. The observed shift with number of walls indicates a change in the strength of the screening and in the effective interaction at inter-atomic distances; thus this result suggests a mechanism for tuning the properties of nanotubes.     

Anchoring of Chiral Manganese(III) Salen Complex onto Organo Clay and Porous Clay Heterostructure and Catalytic Activity in Alkene Epoxidation

The chiral Mn(III) salen complex (C1) was immobilised onto a natural clay (BEN) and a porous clay heterostructure (PCH) functionalised with 3-aminopropyltriethoxysilane (APTES). FTIR, XPS and Mn chemical analysis confirm the C1 anchorage in both materials, but with higher efficiency in BEN_APTES clay. The catalytic activity of C1@BEN_APTES and C1@PCH_APTES, was assessed in the epoxidation of styrene (sty) and ∝-methylstyrene (∝-Mesty) using NaOCl and m-chloroperoxybenzoic acid (m-CPBA)/N-methylmorpholine-N-oxide (NMO). Both materials behave as moderate catalysts, show high epoxide selectivity but low enantiomeric excesses. In the case of sty epoxidation with m-CBPA/NMO the C1@PCH_APTES catalyst showed the highest catalytic activity, whereas in ∝-Mesty epoxidation, the C1@PCH_APTES catalyst, although leading to lower substrate conversion than the BEN analogue, presented the lowest complex leaching. In all cases, the oxidant NaOCl had some destructive effect in the hybrid catalysts, highlighting the importance of a careful choice of catalyst and oxidant system.     

3-D micro-ceramic components from hydrothermally processed carbon nanotube–boehmite powders by electrophoretic deposition

Boehmite/multi-wall carbon nanotube (MWCNT) composite powders were prepared by hydrothermal processing. Starting chemical of aluminum acetate powders (2Al(OH)(C₂H₃O₂)₂) and MWCNTs were mixed for the formation of stoichiometric boehmite powders in an attempt to synthesize MWCNT-reinforced boehmite nano-powders via hydrothermal synthesis at 200 °C for 2 h. Kinetically stable suspensions of MWCNT–boehmite composite powders were prepared and subsequently electrophoretic deposition (EPD) was applied to obtain complex shape products in the form of micro-gears. It is shown that the EPD technique is a powerful tool to manufacture small components in a short time. Detail TEM observations also indicated that hydrothermal processing provides an ideal environment to obtain homogeneous mixtures of MWCNT–boehmite powders due to effective surface functionalization of MWCNTs under hydrothermal conditions.     

MATE-Type Proteins Are Responsible for Isoflavone Transportation and Accumulation in Soybean Seeds

Soybeans are nutritionally important as human food and animal feed. Apart from the macronutrients such as proteins and oils, soybeans are also high in health-beneficial secondary metabolites and are uniquely enriched in isoflavones among food crops. Isoflavone biosynthesis has been relatively well characterized, but the mechanism of their transportation in soybean cells is largely unknown. Using the yeast model, we showed that GmMATE1 and GmMATE2 promoted the accumulation of isoflavones, mainly in the aglycone forms. Using the tobacco BrightYellow-2 (BY-2) cell model, GmMATE1 and GmMATE2 were found to be localized in the vacuolar membrane. Such subcellular localization supports the notion that GmMATE1 and GmMATE2 function by compartmentalizing isoflavones in the vacuole. Expression analyses showed that GmMATE1 was mainly expressed in the developing soybean pod. Soybean mutants defective in GmMATE1 had significantly reduced total seed isoflavone contents, whereas the overexpression of GmMATE1 in transgenic soybean promoted the accumulation of seed isoflavones. Our results showed that GmMATE1, and possibly also GmMATE2, are bona fide isoflavone transporters that promote the accumulation of isoflavones in soybean seeds.     

Methane steam reforming for synthetic diesel fuel production from steam-hydrogasifier product gases

Steam-methane reforming (SMR) reaction was studied using a tubular reactor packed with NiO/γ-Al₂O₃ catalyst to obtain synthesis gases with H₂/CO ratios optimal for the production of synthetic diesel fuel from steam-hydrogasification of carbonaceous materials. Pure CH₄ and CH₄-CO₂ mixtures were used as reactants in the presence of steam. SMR runs were conducted at various operation parameters. Increasing temperature from 873 to 1,023 K decreased H₂/CO ratio from 20 to 12. H₂/CO ratio decreased from 16 to 12 with pressure decreasing from 12.8 to 1.7 bars. H₂/CO ratio also decreased from about 11 to 7 with steam/CH₄ ratio of feed decreasing from 5 to 2, the lowest limit to avoid severe coking. With pure CH₄ as the feed, H₂/CO ratio of synthesis gas could not be lowered to the optimal range of 4–5 by adjusting the operation parameters; however, the limitation in optimizing the H₂/CO ratio for synthetic diesel fuel production could be removed by introducing CO₂ to CH₄ feed to make CH₄-CO₂ mixtures. This effect can be primarily attributed to the contributions by CO₂ reforming of CH₄ as well as reverse water-gas shift reaction, which led to lower H₂/CO ratio for the synthesis gas. A simulation technique, ASPEN Plus, was applied to verify the consistency between experimental data and simulation results. The model satisfactorily simulated changes of H₂/CO ratio versus the operation parameters as well as the effect of CO₂ addition to CH₄ feed.     

Antibacterial poly(vinyl alcohol) film containing silver nanoparticles: Preparation and characterization

The importance of antibacterial materials for biomedical applications is growing nowadays. The presented article deals with the characterization of structural, mechanical and thermal properties and of antibacterial polymeric films based on polyvinyl alcohol (PVA) and silver nitrate, which can find their applicability in wound dressing components and protective coating. The methods of transmission electron microscopy, UV–vis and XRD spectroscopy, optical microscopy, differential scanning calorimetry, stress–strain analysis, and agar diffusion test were used to characterize the polymer films prepared. The results showed strong antibacterial activity against Escherichia coli and Staphylococcus aureus already at the lowest addition level of silver nitrate. An improvement of mechanical properties (Young's modulus) was also noticed due to a modification of PVA with silver nitrate up to 1 wt. % of silver content. Furthermore, the results show a strong effect of the thermal history of the sample preparation on the degree of silver‐ion reduction and formation of nanoparticles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Stability of Fe/ZSM‐5 de‐NOx catalyst: effects of iron loading and remaining Brønsted acid sites

The stability of Fe/ZSM‐5 de‐NOx catalyst has been investigated. The samples are prepared by sublimation of iron chloride. Substantial amount of protons are found to remain in the fresh catalyst after washing and calcination. After 10 h exposure to wet exhaust gas at 600^°C, the catalyst is severely deactivated. The presence of steam induces dealumination of the ZSM‐5 matrix, because the protons provide the point of attack by water. In addition, highly reactive distorted tetrahedral iron species and tetrahedral species change to less reactive octahedral iron ions or iron agglomerates upon aging treatment. With the second sublimation of iron chloride, the iron loading is increased and thus the concentration of remaining protons is reduced. Also, the catalyst turns out to preserve more reactive iron ions after aging treatment. In conclusion, the second sublimation is believed to bring about a remarkable improvement in the stability of the Fe/ZSM‐5 catalyst although its de‐NOx activity is slightly decreased. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tool fabrication for composite forming of aircraft winglet using multi-point dieless forming

Journal of Mechanical Science and Technology - Flexible forming technology such as Multi-point dieless forming (MDF) has benefits for the sheet metal field because it can implement a variety of...