Preparation of TiO 2 nanoparticles in glycerol-containing solutions Tran Trung a,b , Won-Jei Cho b , Chang-Sik Ha b, * a Department of Electrochemistry, Faculty of Chemical Engineering, Hanoi University of Technology, Hanoi, Viet Nam b Department of Polymer Science and Engineering, Pusan National University, Pusan 609-735, South Korea Received 15 November 2001; received in revised form 21 October 2002; accepted 5 November 2002 Abstract TiO 2 nanoparticles were prepared from titanium isopropoxide by using a new solvent system containing glycerol. The particle size by scanning electron microscopy was in the range of 4 –10 nm. The X-ray diffraction data revealed that the nanoparticles possess mostly a tetragonal crystal structure of anatase. The absorption of the tetrahedral titanium species at 280 nm on UV spectra exhibited the quantum size effect of the nanoparticles. D 2002 Elsevier Science B.V. All rights reserved. Keywords: TiO 2 ; Nanoparticles; Glycerol; Anatase; Sol – gel method; Characterization 1. Introduction Nanometer-sized titanate particles have been inten- sively studied because of their versatile applications, for example, in photocatalysis, optical coatings and optoelectronic devices [1–7]. The formation of nano- particles by the sol – gel method has been reported to be strongly dependent on the choice of a solvent and a foreign stabilizing surfactant [2,8–17] such as poly (ethylene glycol) (PEG) and 2-(2-methoxyethoxy) ethanol. By using PEG as a stabilizer, for instance, particle size can be controlled and decreased to 10 – 15 nm [8,12]. With the same solution system but without the stabilizer PEG, however, the particle size is mark- edly dependent on the heating temperature and even it may be up to 50 nm at 650 jC [12]. This study attempts to find a new stabilizer and a solvent system to obtain nanoparticles more easily. We wish here to report on the preparation of TiO 2 nanoparticles by using a new solvent system that is different from other conventional stabilizer-free sol- vents such as water and different types of alcohol and acid, in which a solution containing glycerol is used. 2. Experimental TiO 2 nanoparticles were prepared by hydrolyzing titanium isopropoxide, Ti(i-Pro) 4 (purity 99.999%), in different solvent systems with or without glycerol (purity 99.5%, spectrophotometric grade). Samples Sp1, Sp2 and Sp3 were prepared from stock solutions including a solution mixture containing absolute alco- hol (purity 99.5%, A.C.S. grade) and acetic acid 0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0167-577X(02)01369-1 * Corresponding author. Tel.: +82-51-510-2407; fax: +82-51- 514-4331. E-mail address: csha@pnu.edu (C.-S. Ha). www.elsevier.com/locate/matlet Materials Letters 57 (2003) 2746 – 2750