2. Experiments2.1. Preparation of T

2. Experiments
2.1. Preparation of TiO2 precursor sol
All the chemicals were purchased from Merck and used as
received without any further purification. Deionized (DI) water that
was prepared by an ultra pure water system type smart-2-pure,
TKA, Germany, was used throughout.
The TiO2 sol was prepared by hydrolyzing tetrabutyl ortho
titanate (TBOT) in acidic conditions. In this method, 2.5 ml TBOT,
10 ml Ethanol and 2.5 ml acetylacetone (acac) were mixed. Acac
was used as chelating agents to prevent from precipitation of the
TBOT. After stirring with magnetic force for 30 min, the clear and
yellow solution was obtained. We then added 2.0 ml DI water to
the above solution and stirred the mixture for 10 min. A few drop
of concentrated HCl solution was then added to the sol to adjust
the pH at about 1.8.