Analysis of colorimetry using the CIE-Lab system and the photocatalytic activity of photochromic films

[Display omitted] •The films containing fibers were efficient in the degradation of methyl orange dye.•Doping of TiO2 with W allowed the band gap reduction of TiO2.•The photochromism observed in the films was due to the synchronicity between oxides.•The films exhibited variations between colors, and different reflectance levels. This work aims to explain how oxide films are correlated when exposed to UV-A radiation, due to the occurrence of similar phenomena. Thus, thin films of TiO2 and TiO2 doped with H2WO4 or Na2WO4·2H2O were made by spin-coating, heat treated between 650 and 800 °C and evaluated for their optical and photocatalytic properties. The X-ray diffraction technique (XRD) was used to determine the crystalline structure of the films. The photochromism was observed through a spectrophotometer using the CIE-Lab colorimetric method. The analysis of the films photocatalytic behavior was obtained following the photodegradation in 125 ml of methyl orange dye (20 ppm). The results showed that the films presented good photochromic and photocatalytic properties due to the synchronization between the chemical and physical properties of TiO2 and tungsten.