Optical constants, photo-stability and photo-degradation of MB/PMMA thin films for UV sensors

The effect of different light wavelengths on methylene blue dye doped poly(methyl methacrylate) thin films during casting was investigated. The colour of the thin films which casted under the light sources of short wavelength ultraviolet light (254 nm), long wavelength ultraviolet light (367 nm) and sunlight were compared with the film casted in the dark. UV–vis spectrometer was used to measure the transmittance and absorbance of the fabricated films, and moreover, band gap energies were calculated. Results show that the wavelength of the applied light influences on the colour stability of methylene blue due to the photolysis of poly methyl methacrylate or chloroform (solvent). The highest decolourization rate was observed under the illumination of 254 nm, in which 90% of the colour was discharged after 30 min of illumination's time. However, no colour change was observed when the thin films were kept in dark during the casting step.