title: Dispersion stability of TiO2 nanoparticles covered with SiOx monolayers in water.
abstract: The repetition of a two-step route consisting of chemisorption of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) and its subsequent photooxidation has formed SiOx monolayers on the surfaces of TiO2 particles layer by layer (SiOx(n < or = 4)/TiO2, n = repeated number). The trace of these processes using diffuse reflectance FT-IR and solid-state 29Si NMR spectroscopy reveals that TMCTS is chemisorbed on TiO2 through Ti-O-Si bonds followed by growth of Si-O-Si networks via dehydration-condensation of the Si-OH groups generated by TiO2 photocatalytic oxidation of the Si-H and Si-CH3 groups. The point of zero charge of the TiO2 particles decreases from 6.5 to 5.4 at n = 1, reaching 4.9 at n2. As a result of coverage with the SiOx monolayers, the dispersion stability of TiO2 particles in neutral water is significantly improved without changing their optical properties. The dispersion stability further increases with accumulation of SiOx monolayers.
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan. h-tada@apch.kindai.ac.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tada
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishio
authors.forename: Naoko
authors.initials: N
authors.lastname: Kubo
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsui
authors.forename: Masakuni
authors.initials: M
authors.lastname: Yoshihara
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Kawahara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukui
authors.forename: Seishiro
authors.initials: S
authors.lastname: Ito