Dispersion stability of TiO2 nanoparticles covered with SiOx monolayers in water

Hiroaki Tada; Osamu Nishio; Naoko Kubo; Hideo Matsui; Masakuni Yoshihara; Tetsuro Kawahara; Hiroshi Fukui; Seishiro Ito

doi:10.1016/j.jcis.2006.10.006

Dispersion stability of TiO2 nanoparticles covered with SiOx monolayers in water

J Colloid Interface Sci. 2007 Feb 15;306(2):274-80. doi: 10.1016/j.jcis.2006.10.006. Epub 2006 Nov 27.

Authors

Hiroaki Tada¹, Osamu Nishio, Naoko Kubo, Hideo Matsui, Masakuni Yoshihara, Tetsuro Kawahara, Hiroshi Fukui, Seishiro Ito

Affiliation

¹ Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan. [email protected]

PMID: 17125784
DOI: 10.1016/j.jcis.2006.10.006

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.