Dispersion stability of TiO2 nanoparticles covered with SiOx monolayers in water

• Published in: Journal of colloid and interface science Vol. 306; no. 2; pp. 274 - 280
• Main Authors: TADA, Hiroaki, NISHIO, Osamu, KUBO, Naoko, MATSUI, Hideo, YOSHIHARA, Masakuni, KAWAHARA, Tetsuro, FUKUI, Hiroshi, ITO, Seishiro
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier 15-02-2007
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Water; Monolayer; Stability; Nanoparticle; TiO2 particles; Photocatalysis; Dispersion stability; Transition element compounds; 29Si NMR; NMR spectrometry; Dispersion; Particle; SiOx monolayer; Titanium oxide
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2006.10.006

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.