Two factors including annealing temperature and number of
cycle dip coating of thin films were also investigated to evaluate
the best condition for degradation efficiency of MO solution under
visible light irradiation and the results were shown in Fig. 10. It
is found that at temperature 300 and 400 ◦C photocatalytic activity
is very poor and optimal photocatalytic efficiency is obtained
at 500 ◦C (Fig. 10(a)). The melting glass slides temperature is above
than 600 ◦C, therefore we cannot consider the higher temperatures.
Therefore, the Tu/PEG–TiO2 calcined at 500 ◦C owns the highest
photocatalytic activity. Fig. 10(b) shows the influence of number
of cycle dip coating of thin films to degradation of MO solution
under visible light. It is found that the samples with 5, 10, 15 and
20 times dip coating, exhibit the similar photocatalytic activity and
only photoactivity of thin film with once dip coating became less.