Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (11): 1274-1279.doi: 10.3866/PKU.WHXB20051116

• ARTICLE • Previous Articles     Next Articles

Effect of Halides on Photo-induced Hydrophilicity over TiO2 Films

DAI Wen-xin; WANG Xu-xu; FU Xian-zhi; LIU Ping; LIN Hua-xiang   

  1. Research Institute of Photocatalysis, Fuzhou University, Fuzhou 350002
  • Received:2005-03-22 Revised:2005-06-20 Published:2005-11-15
  • Contact: WANG Xu-xu E-mail:xwang@fzu.edu.cn

Abstract: A series of TiO2-X films doped with different halides X(I, Br, Cl, and F) coated on the slide was prepared by dip-coating in the TiO2 sol into which potassium halide (including KI, KBr, KCl and KF) was introduced. The photo-induced hydrophilicity of TiO2-I films with different contents I was investigated by testing the change of water contact angle on film’s surface with UV light irradiation time, so was the changes in photoinduced hydrophilicity of TiO2 films containing different halides. Then, the durability of the TiO2-X films was investigated by testing the change of water contact angle with dark storage time. Firstly, this result shows that the photo-induced hydrophilic property of TiO2 films could be enhanced by introducing a little KI into TiO2 sol, at the best with KI content of 1.0×10-5 mol•L-1. However, with the further increase of KI, the photo-induced hydrophilic property of TiO2-I films would decrease, and even worse than that of pure TiO2 films when the KI contents is 1.0×10-2 mol•L-1. Secondly, introducing KBr and KCl of 1.0×10-5 mol•L-1 into TiO2 sol could also enhance the photo-induced hydrophilicity of TiO2 films in an order of KI>KBr>KCl, but introducing KF decreased that of TiO2 films. Finally, introducing KX (KI and KF) could increase durability of hydrophilicity of TiO2 films under dark storage condition, and KF shows a better effect than KI. Based on these results, it is suggested that the halides act as electron donors or scavengers to affect the photo-induced hydrophility of TiO2 films, and the mechanisms of photo-induced hydrophilicity of TiO2-X films is proposed. However, the higher durability of hydrophilicity of TiO2-X films compared with pure TiO2 films may be due to a great stability of hydrophilicity site Ti—OH, which is caused by the strong binding action (hydron bond) between Ti—X and Ti—OH.

Key words: Photo-induced hydrophilicity, TiO2 films, Potassium halides, Electron donor, Electron scavenger