Dosimetric characterization of novel polycarbonate/porphyrin film dosimeters for high dose dosimetry. Study on complexation effect

Two novel radiochromic films with 20 μm thickness were made from casting of solutions of polycarbonate (PC) containing 0.5 wt.% tetra phenyl porphyrin (TPPH₂) and 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe-TPP). Dosimetric characterization of the films as routine dosimeters were studied by spectrophotometric method. On subjecting TPPH₂/PC and Fe-TPP/PC film dosimeters to gamma radiation, radiolytic bleaching of films was observed. The effects of metal-complexation on the radiation response of the film dosimeters were studied under ⁶⁰Co γ-rays exposure in dose range of 0-100 kGy. The results were also compared with the PC/TPPF₂₀ (PC/tetrakis (pentafluorophenyl) porphyrin) dosimeter to evaluate the substituent effect (role of fluorine groups). Experimental parameters including humidity, temperature and pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were examined. The maximum absorbance of Soret band of dyes had meaningful shifts and reduction which arose from complexation and substituents. The dyed films characteristics were found to be stable enough in media with high degrees of temperature and humidity. The results indicate that the radiation-induced decoloration of TPPH₂/PC and Fe-TPP/PC films can be reliably tuned and used in high dose dosimetry.