*2.4. Photocatalytic Characterization of Coatings*

The photocatalytic activities of the coatings were analyzed using the methylene blue (MB) degradation assay under UV and fluorescent light sources. In brief, MB solutions were made up to an initial concentration of 0.0105 mMol·L<sup>í</sup><sup>1</sup> . Photocatalytic surfaces were placed in 10 mL of the MB solution and irradiated at an integrated power flux of 40 W/m2 with two 15 W UV lamps (365 nm wavelength). Tests were also carried out using two 15 W fluorescent tubes in place of the UV tubes to simulate typical lighting environments. The integrated power flux to the coatings with the fluorescent tubes was 64 W/m2 , of which the UV component (300–400 nm) was 13 W/m2 . A 10 cm distance between the light source and MB solution was used. Samples of the MB solution were taken before testing and at 1 hour intervals up to a total of 5–8 h. and analyzed using a UV-Vis spectrophotometer (Perkin Elmer, Waltham, MA, USA). Spectra were taken in the range of 650–668 nm and the height of the absorption peak in this region was monitored.

A graph of peak height absorbance against irradiation time, which has an exponential form was generated. An index of photocatalytic activity (*Pa*) was defined by comparing the degradation rate of the MB solution in contact with the coated surfaces to the rate for an irradiated MB solution with no coating present. The equation below was used to calculate the photocatalytic activity of each of the films. Two parameters were defined: *Pa*UV for UV irradiation and *Pa*FL for fluorescent light irradiation [28].

$$Pa = 1 - C\_0 \left[ \mathfrak{e}^{-m} \bigvee\_{\mathbf{e} \in \mathbb{C}^m} \right] \tag{l}$$

where *C*0 = peak height at time = 0; *C*0e<sup>í</sup>*mx* = decay rate of methylene blue; *C*0e<sup>í</sup>*cx* = decay rate of methylene blue in contact with photocatalytic coating.
