Modifications of the optical properties in Makrofol-E SSNTD exposed to ultraviolet radiation of different wavelengths

The induced modifications of the optical properties in UV-irradiated Makrofol-E with different wavelengths were investigated. Makrofol-E samples were irradiated by UV of wavelengths 254, 302, and 365 nm for different durations. It was found that Makrofol-E shows substantial modifications in its optical characteristics upon exposure to UV of wavelengths 302 and 254 nm, but no modifications were observed at 365 nm. UV-irradiated Makrofol-E with wavelengths 254 and 302 nm exhibits shoulder bands at 297 nm in UV-visible spectra. For an exposure time less than 20 h, the band absorbance strengths depend on the exposure time and approximately increases linearly, but for prolonged exposure times, the band absorbance strengths become almost saturated. The optical energy band gaps obtained from the direct and indirect allowed transition in K-space. Both of them decrease with the increase in exposure time for wavelengths of 254 and 302 nm. Urbach's energy increases with increase in the exposure time for both wavelengths of 254 and 302 nm. The number of carbon atoms in a cluster increases with the increase in the exposure time.