title: Synthesis of Silica Nanotube Using Myelin Figure as Template and their Formation Mechanism.
abstract: Silica nanotubes are synthesized through a sol-gel reaction of tetraethyl orthosilicate (TEOS) using myelin figures of Pluronic P123 as the structure-directing agent. The simultaneous progression of the formation of molecular assemblies that act as templates and the formation of silica frameworks though a sol-gel reaction of the silica precursor is a characteristic of this reaction system. The synthesized silica nanotubes were characterized using transmission electron microscopy (TEM), nitrogen adsorption/desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). The silica nanotubes were unilamellar with diameters of approximately 30 nm, membrane thicknesses of approximately 10 nm, and lengths exceeding a few hundred nanometers. The Brunauer-Emmett-Teller (BET) specific surface area was 589.46 m(2)/g. Silica nanotubes can also be obtained using other Pluronic surfactants that can form myelin figures. In this work, we also investigated the formation mechanism of the silica nanotubes. The typical diameter of a myelin figure is a few tens of micrometers. However, myelin figures with diameters of approximately 10 µm can form in systems with TEOS because bifurcation is induced by minute silica nuclei that form during the initial reaction between TEOS and water. Freeze fracture TEM (FF-TEM) observations revealed the existence of myelin figures with diameters of 20 to 30 nm, which are the same size and shape as the synthesized silica nanotubes. These results indicate that bifurcation of the myelin figures is induced by the silica nuclei that form via the initial reaction of TEOS, which result in the formation of bifurcated myelin figures with diameters of ~10 µm. Myelin figures with diameters of 20 to 30 nm form on the surface, and they become templates where the reaction of TEOS progresses to form silica nanotubes with diameters of approximately 30 nm.
authors.affiliation: Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science.
authors.forename: Takumi
authors.initials: T
authors.lastname: Fukamachi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Endo
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Yabuki
authors.forename: Taku
authors.initials: T
authors.lastname: Ogura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Misono
authors.forename: Kanjiro
authors.initials: K
authors.lastname: Torigoe
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sakai
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abe
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
mesh_terms: D005614:Freeze Fracturing; D046529:Microscopy, Electron, Transmission; D009186:Myelin Sheath / Q000737:chemistry*; D043942:Nanotubes; D010316:Particle Size; D044367:Phase Transition; D011060:Poloxalene / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry*; D012822:Silicon Dioxide / Q000138:chemical synthesis* / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D012821:Silanes; C464484:pluronic block copolymer P123; C040733:tetraethoxysilane; D012822:Silicon Dioxide; D011060:Poloxalene