Koji Nakane

Entrap-immobilization of biocatalysts on cellulose acetate-inorganic composite gel fiber using a gel formation ofcellulose acetate–metal (Ti, Zr) alkoxide

We developed a new entrap-immobilization method, using a gel formationof cellulose acetate and metal (Ti, Zr) alkoxide. Several biocatalysts(β-galactosidase, α-chymotrypsine, invertase, urease, lipase andSaccharomyces cereviciae) were successfullyentrap-immobilized on this composite gel fiber. The immobilization process wassimple and the resultant immobilized biocatalysts on the gel fiber were easy tohandle. It is considered that the biocatalysts are physically entrapped amongthe gel networks and distribute throughout the gel fiber. The gel fiber wasstable in phosphate buffer solution, electrolyte solution and organic solvent,because the gel formation was due to coordination interaction between celluloseand transition metal. Therefore, it can be applicable as a support for abiotransformation in various reaction media. We examined some enzyme reactionsand biotransformation using the immobilized biocatalysts on this gel fiber andevaluated this immobilization matrix in the reactions compared to the resultsobtained by the other immobilization method. The immobilized biocatalyst showedstable activity for repeated cycles and over a long period of time. Moreover,continuous reaction could be carried out in a column reactor packed with thisimmobilized biocatalyst.

Thoroughly mesoporous TiO2 nanotubes prepared by a foaming agent-assisted electrospun template for photocatalytic applications

A thoroughly mesoporous long TiO2 nanotube with intact morphology was firstly prepared using a foaming agent-assisted electrospun template method in which an electrospun water-soluble PVA nanofiber was used as the template. The large volumes of vapors released from the introduced foaming agents are attributed to the production of mesopores with uniform spatial distribution on the whole TiO2 tube wall and these mesopores prevent damage to the TiO2 nanotubular morphology during the PVA template removal. The present work represents a critically important solution in advancing the electrospinning technique for generating mesoporous nanotubes in an effective and facile manner.

Photocatalyst Nanofibers Obtained by Calcination of Organic-Inorganic Hybrids

Electrospinning (ES) is one of the most useful techniques to form nanofibers in a diameter of several hundred nanometers (Doshi & Reneker, 1995, Buchko et al., 1999, Huang et al., 2003). The diameter of the nanofibers produced by ES is at least one or two orders of magnitude smaller than those of conventional fiber production methods like melt or solution spinning. As a result, the electrospun nanofibers have high specific surface area (Yamashita, 2007). These nanofibers are well-suited to be used as chemical reaction fields (Nakane et al., 2005, 2007). Much attention has been paid to the formation of both organic polymeric nanofibers and inorganic nanofibers using ES (Ramakrishna et al., 2005). Many kinds of inorganic nanofibers (SiO2, Al2O3, ZrO2, NiCo2O4, and so on) have been obtained by calcination of organic-inorganic hybrid precursor nanofibers formed by ES (Guan et al., 2004, Shao et al., 2004, Chronakis, 2005, Panda & Ramakrishna, 2007, Krissanasaeranee et al., 2008). The formation of TiO2 nanofibers have been also reported by several research groups. Li and Xia formed anatase-type titanium oxide (TiO2) nanofibers by the calcination of poly(vinyl pyrrolidone) (PVP)-Ti tetraisopropoxide (TTIP) hybrid nanofibers at 500°C in air (Li & Xia, 2003). The TiO2 nanofibers obtained would be a useful material for a photocatalytic reaction, but their usage has not been investigated. Ethanol has been used as the solvent of the spinning solution to form the hybrid precursor nanofibers. Therefore, a spinneret could be stopped up by a solid material because ethanol will evaporate from the tip of the spinneret during the spinning. Furthermore, TTIP is very easily hydrolyzed, and thus a water-free condition is required for the use of TTIP on ES. Another groups also formed TiO2 nanofibers by calcination of TiO2-PVP and TiO2-poly(vinyl acetate) precursors which were formed by ES using organic solvents such as ethanol and dimethylformamide (Kim et al., 2006, Nuansing et al., 2006, Kumar et al., 2007, Ding et al., 2008). Li and Xia reported the formation of TiO2 hollow-nanofibers (nanotubes) by ES of two immiscible liquids (TTIP-PVP ethanol solution and heavy mineral oil) through a coaxial, two-capillary spinneret, followed by selective removal of the cores and calcination in air (Li & Xia, 2004). The TiO2 nanotubes with uniform and circular cross-sections were obtained by the method. Kobayashi et al. reported the preparation of TiO2 nanotubes using the gelation (self-assembly with a rodlike fibrous structure) of an organogelator (It is not ES.) (Kobayashi et al., 2000, 2002). The organogelator is a cyclohexane derivative that was specially Source: Nanofibers, Book edited by: Ashok Kumar, ISBN 978-953-7619-86-2, pp. 438, February 2010, INTECH, Croatia, downloaded from SCIYO.COM

Formation of niobium oxide and carbide nanofibers from poly(vinyl alcohol)/niobium oxide composite nanofibers

Poly(vinyl alcohol)-niobium oxide (Nb2O5) composite nanofibers (precursors) were formed by electrospinning employing water as a solvent for the spinning solution. The precursors were converted into Nb2O5 or carbide (NbC) nanofibers by heating them in air or Ar. Hexagonal Nb2O5 nanofibers with high-specific surface area were obtained by heat-treatment of the precursors in air. NbC nanofibers could be obtained below theoretical temperatures calculated from thermodynamics data, indicating that the precursor is a nano-scale mixture of Nb and carbon sources.

Synthesis and Characterization of Li[Ni(1/3-x)Mn(1/3-x)Co(1/3-x)Mx]O2(M=Fe,Mg,Al) Particle by Aerosol Process

Spherical Li[Ni(1/3-x)Mn(1/3-x)Co(1/3-x)Mx]O2 (M=Fe, Mg, Al) precursor powders were synthesized by ultrasonic spray pyrolysis using aqueous solution of metal nitrate. X-ray diffraction (XRD), scanning electron microscope (SEM), BET method using N2 adsorption analysis and Battery tester were used for determination of the composition, morphology, particle size, surface area and electrochemical properties. SEM observation showed that the size of as-prepared particles were about 0.9 μ with narrow size distribution. The crystal phase of Li[Ni(1/3-x)Mn(1/3-x)Co(1/3-x)Mx]O2 (M=Fe, Mg, Al) was resulted in layered rock salt structure with R3m space group by calcinations at 1023 K for 10 h. No impurity-related peaks are observed from the XRD pattern with various doping metals. Mg and Al doped Li(Ni1/3Co1/3Mn1/3)O2 showed very good cycling stability. The Mg substitution for Ni led to the most excellent. On the other hand, the capacity degradation during cycling was observed by Fe substitution for Mn doped Li(Ni1/3Co1/3Mn1/3)O2.

Synthesis and Characterization of BaTiO3 Nano-Particle by Aerosol Plasma Pyrolysis Process

Homogeneous BaTiO3 nano-sized powders were successfully prepared by spray pyrolysis using multiphase plasma under the air atmosphere. Particle size, morphology, crystal phase and crystallinity of as-prepared powders were characterized by SEM and XRD. The effect of starting precursor solution on the formation of nanoparticles was investigated. The use of Ba/Ti aqueous solution derived from malic acid led to formation of cubic BaTiO3 nanoparticles with 50 nm size.

Effect of melt and solution electrospinning on the formation and structure of poly(vinylidene fluoride) fibres

We investigated the effects of applied voltage and collector rotating speed on the crystal structure and piezoelectricity of poly(vinylidene fluoride) (PVDF) fibres obtained by two electrospinning (ES) systems; laser-melt electrospinning (M-ES) and conventional solution electrospinning (S-ES). A higher β phase fraction was observed in the S-ES fibres, although the M-ES fibres showed comparable crystallinity. The piezoelectric constant (d33) for the S-ES fibres was also higher than that of the M-ES fibres. This is the first report clarifying the difference between M-ES and S-ES for the formation of PVDF fibres.

Structural analysis of cellulose acetate and zirconium alkoxide hybrid fibres

We investigated the detailed structures of organic–inorganic hybrid fibres composed of cellulose acetate (CA) and zirconium alkoxides (Zr(OR)4) using attenuated total refraction-Fourier transform infrared spectroscopy (ATR-FTIR), energy-dispersive X-ray spectroscopy (EDS), and X-ray absorption fine structure (XAFS) measurements. The fibres were prepared by an air-gap spinning technique, where the acetone solution of CA was injected into a Zr(OR)4–acetone bath. The Zr contents in the prepared fibres increased with increasing Zr(OR)4 bath concentration, but reached steady-state values at Zr(OR)4 bath concentrations above 10 wt%. In addition, EDS analysis for the cross-section of the fibre showed that Zr distribution in the fibre varied depending on Zr(OR)4 bath concentration and alkoxide type. ATR-FTIR and XAFS analysis showed that Zr contained in a CA fibre was hexacoordinated, with a local structure similar to that of hydrolysed Zr(OR)4. This result indicated that the confinement to the CA fibre had little influence on the local structure of Zr.

Poly(vinyl butyral)-zirconia hybrid films formed by sol-gel process

A sol-gel process has been successfully utilized to form hybrid materials of poly(vinyl butyral) (PVB) and zirconium dioxide (zirconia). The gelation occurred due to the interaction between remaining hydroxyl group of PVB and zirconia. The hybrids showed good optical transparency and significant improvement in Youngs modulus, dynamic mechanical property, abrasion resistance and impact resistance. The glass transition temperature of PVB shifted to higher temperatures by hybridization of PVB and zirconia.

Development of superamphiphobic alumina nanofiber mats using trimethoxysilane with a short perfluoroalkyl chain

To avoid the generation of hazardous, long-chain perfluoroalkyl carboxylic acids (C n F2 n +1COOH, n ≥ 7), we develop relatively safer superamphiphobic alumina nanofiber mats. Our fabrication process focuses on two principles: lowering the surface energy using trimethoxy(1H, 1H, 2H, 2H-nonafluorohexyl)silane (C4F9CH2CH2Si(OCH3)3), which has short-chain perfluoroalkyls that are relatively safer than long-chain ones; and creating a high-roughness surface from electrospun alumina nanofibers with an average fiber diameter of 155 nm and inter-fiber spacing of 451 nm. Such mats exhibit super-repellency for water (contact angle θ *  = 157°, contact angle hysteresis Δ θ * = 2 ∘ , advancing angle θ adv * = 158°, receding angle θ rec * = 156°), and n-hexadecane ( θ *  = 151°, Δ θ * = 9°, θ adv * = 152°, θ rec * = 143°). Furthermore, superamphiphobicity is maintained up to 350℃.