The pictures of stained samples were obtained by a scanner
(Fig. 2a). Non-treated nylon fabric was used as controls. The azo
dye used in this study was anionic dye and was negatively charged
because of the sulfonate groups (Fig. 1). Accordingly, electrostatic
interactions between the photocatalysts surface (Ti3+ or Zn2+) and
dye anions lead to the formation of adsorption. The staindegradability
of treated fabrics was enhanced compared to the
control sample (Fig. 2a). This can be due to the generation of highly
oxidative species decomposing dye molecules on treated samples.
Since azo bonds are the chromophores contributing to color of azo
dyes, decolorization of the azo dyes is very likely influenced by the
number of azo bonds present in a dye molecule. Generally
speaking, trisazo dyes like Direct Green 6 are refractory [37].
Fig. 2b shows the comparison diagram achieved from spectrophotometer
results of raw and coated nylon fabrics. No noticeable
dye degradation was seen on the control sample after 6 h radiation.
The results acquired indicate that the coated sample with nylon
nanofibers containing 0.2% SrTiO3/0.3% TiO2 concentration ratio of
nanophotocatalysts (Fig. 2b, D) had the highest discoloring level.
Observed superior photoactivity of nanofibers containing TiO2/
SrTiO3 is thought to be explained on the basis of the increase in
charge separation efficiency, and exited electrons in conduction
band of TiO2 by UV irradiation being injected to conduction band of
SrTiO3 to suppress recombination between the electrons and holes
in TiO2