2.1. Preparation of the TiO2 substrates
All of the chemicals were purchased and used without
further purification. First, tetrabutyl titanate was added into
ethylalcohol with stirring for 30 min, followed by adding
diethanolamine dropwise to form solution A. Deionized water
was dissolved into ethylalcohol under magnetic stirring to
form solution B. Then, solution B was added dropwise into
solution A with stirring for 2 h, followed by stewing the
mitxure for 4 h. The molar ratio of tetrabutyl titanate,
ethylalcohol, deionized water and diethanolamine was
1: 26.5:1:1. Finally the mixture was homogeneous coated on
cleaned glass substrate with pulling rate at 20 mm/s and then
sintered at 550 1C for 2 h to form the TiO2 substrates.