Determining the photocatalytic power of TiO2 powders is not
trivial,25 so students needed to assess the advantages and
limitations of the various techniques available for this analysis.
On the basis of the reagents and facilities available in the
laboratory, students decided to evaluate the photocatalytic
activity of titania powders by the degradation of an organic dye,
toluidine blue, under a 365 nm UV lamp. Toluidine blue is
soluble in water and has a strong absorption peak at 630 nm, so
the photodegradation process can be easily followed by
measuring the dye concentration using UV−vis spectrophotometry.
The items shown in Figure 1A, namely, a cardboard
box, tape, a black bin liner, a cutter, and a UV lamp, were given
to each group of students to fabricate a test chamber. This
chamber is needed to prevent interference from external light
sources, which may affect the measurement results. A simple
test chamber constructed by the students is shown in Figure
1B.