tailieunhanh - Nanofibers_2

“There’s Plenty of Room at the Bottom” ⎯ this was the title of the lecture Prof. Richard Feynman delivered at California Institute of Technology on December 29, 1959 at the American Physical Society meeting. He considered the possibility to manipulate matter on an atomic scale. Indeed, the design and controllable synthesis of nanomaterials have attracted much attention because of their distinctive geometries and novel physical and chemical properties. For the last two decades nano-scaled materials in the form of nanofibers, nanoparticles, nanotubes, nanoclays, nanorods, nanodisks, nanoribbons, nanowhiskers etc | 11 Photocatalyst Nanofibers Obtained by Calcination of Organic-Inorganic Hybrids Koji Nakane and Nobuo Ogata University of Fukui Japan 1. Introduction 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