Direct synthesis of Te/Bi2Te3 nanocomposite powders by a polyol process

Research on Chemical Intermediates - Tellurium nanotube-based bismuth telluride (Te/Bi2Te3) nanocomposite powders have been synthesized by the polyol process using Bi (NO3)3, TeCl4 as the metal...     

Synthesis of reversible fluorescent organogel containing 2-(2′-hydroxyphenyl)benzoxazole: fluorescence enhancement upon gelation and detecting property for nerve gas simulant

A new low molecular mass organogelator 1 containing 2-(2′-hydroxyphenyl)benzoxazole (HPB) group with long alkyl chain was synthesized by the reaction with 5-amino-2-(2′-hydroxy-4′-methylphenyl)benzoxazole and dodecyl isocyanate in THF at room temperature. The reversible gelation ability of 1 was investigated using a heating-cooling method in various organic solvents. The stable organogel was formed from carbon tetrachloride or from cyclohexane at the concentration as low as 0.9%. The self-assembled supramolecular gel structure formed by non-covalent bonding was confirmed with field emission-scanning electron microscope (FE-SEM) exhibiting fibril- or ribbon-shaped structure depending on the solvent used. Regarding the aggregation-induced emission enhancement (AIEE) phenomenon, the optical properties were investigated in its solution and gelled state. The detecting properties of resulting organogel toward nerve gas simulant were monitored by UV-vis and fluorescence spectroscopy. Both color change from colorless to greenish yellow and disruption of gel structure resulting from alteration in intermolecular forces were observed upon the exposure to nerve gas simulant.     

Development of Batch and Continuous Processes on Biodiesel Production in a Packed-Bed Reactor by a Mixture of Immobilized Candida rugosa and Rhizopus oryzae Lipases

In this study, transesterification and esterification were investigated in batch and continuous process using immobilized Candida rugosa and Rhizopus oryzae lipases. In the case of batch process, stepwise reaction method was investigated to prevent the lipase deactivation. Reaction conditions were as follows: temperature, 45 °C; agitation speed, 250 rpm; enzyme concentration, 20%; and water contents 10%. And then, conversion yield was 98.33% at 4 h. In the case of continuous process, circulation and long-term continuous system were investigated for development of efficient mass transfer system. Optimal reaction conditions were as follows: temperature, 45 °C; flow rate, 0.8 mL/min; and water contents, 10%. And then, conversion yield of biodiesel was 97.98% at 3 h. Especially, the maximum conversion yield using a mixture of immobilized lipases exceeded over 90% for 108 h in long-term continuous system under optimal reaction conditions (45 °C; flow rate, 0.8 mL/min; and water contents, 10%). These results should help in determining the best method for the biodiesel production and improving the design and operation of large scale by enzymatic systems.     

Synthesis of poly(p‐phenylenediamine‐ co‐o‐aminophenol)/multi‐walled carbon nanotube composites by emulsion polymerization

Organic–inorganic composites composed of electrically conducting copolymer p‐phenylenediamine‐ co‐o‐aminophenol and carboxylic acid functionalized multi‐walled carbon nanotubes [poly(pPD‐co‐oAP)/c‐MWNTs] were prepared via in situ emulsion pathway using sodium dodecyl sulphate (SDS) as an emulsifier and potassium persulphate as an oxidant. Acid functionalized MWNTs were used as cores in the formation of tubular shells of the composites. TEM and FESEM analysis showed that a tubular layer of coated copolymer film of several nanometer thicknesses is present on the c‐MWNTs surfaces. FT‐IR spectra endorsed the formation of composites. TGA results indicated that the decomposition temperatures of composites were higher than the bare copolymer. UV‐visible absorption spectra of diluted colloidal dispersion of composites were similar to those of the bare copolymer. The composites were also confirmed by XRD and XPS. Room‐temperature conductivity increases with an increasing fraction of c‐MWNTs. Copyright © 2009 John Wiley & Sons, Ltd.     

Engineering enzyme specificity using computational design of a defined-sequence library

Engineered biosynthetic pathways have the potential to produce high-value molecules from inexpensive feedstocks, but a key limitation is engineering enzymes with high activity and specificity for new reactions. Here, we developed a method for combining structure-based computational protein design with library-based enzyme screening, in which inter-residue correlations favored by the design are encoded into a defined-sequence library. We validated this approach by engineering a glucose 6-oxidase enzyme for use in a proposed pathway to convert D-glucose into D-glucaric acid. The most active variant, identified after only one round of diversification and screening of only 10,000 wells, is approximately 400-fold more active on glucose than is the wild-type enzyme. We anticipate that this strategy will be broadly applicable to the discovery of new enzymes for engineered biological pathways.     

Passive regulation of volume‐flow ratio for microfluidic streams with different hydrophilicity and viscosity

Biochemical solutions have a wide range of hydrophilicity (contact angle and surface tension) and viscosity. A critical challenge is that microfluidic systems typically need expensive or complex pumps to control the various parallel biochemical streams. In this study, without using any pumps, we present a simple scheme that controls the ratio of the volumetric flow rate (VFR) of the parallel streams that have highly different hydrophilicity and viscosity. We accomplish this process by using capillarity to drive and merge two streams, and by regulating relative flow resistance to control the VFR ratio. Our results will significantly simplify the control of the VFR ratio for the various biochemical solutions that are used in microfluidic applications.     

Characteristics analysis of hybrid plasmonic waveguide for low-loss lightwave guiding

It has been experimentally demonstrated that a low-loss guided hybrid mode is supported if a metal strip is embedded in a low index polymer layer surrounded by two high index slabs. In this paper, further numerical analyses on the guided hybrid modes are reported to fully elucidate the characteristics of the hybrid plasmonic waveguide. For a one-dimensional slab structure with a metal film of infinite width, simulation results exhibit that low-loss guided hybrid modes are associated with surface plasmon modes and dual dielectric slab modes. The optical properties of the guided modes are improved by increasing the field intensity which is confined into lossless dielectric layers by decreasing the metal film thickness and increasing the refractive index and thickness of the high-index slabs. The finite element method is used to investigate the lateral mode confinement of the optical guided modes by the corresponding metal strip. By reducing the metal film width, the guided modes are confined in the plane transverse to the direction of propagation and the characteristics are significantly improved. The hybrid plasmonic waveguide can be exploited for long-range propagation-based application such as optical interconnection.     

Observation of mechanical fracture and corresponding domain structure changes of polycrystalline PbTiO3 nanotubes

PbTiO₃ (PTO) nanotubes (NTs) were synthesized at various temperatures by gas phase reaction between PbO gas and anatase TiO₂ NTs and characterized by piezoresponse force microscopy (PFM). PTO ferroelectric phase was synthesized at as low as 400 °C as evidenced by PFM domain images and piezoresponse hysteresis loop measurement. Furthermore, the PTO NTs fabricated at above 500 °C underwent mechanical fracture through development of nanocracks due to grain growth, leading to ferroelectric domains with larger size and lower aspect ratio. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)