Polymer gel has been used as a dosimeter to determine spatial dose distributions by radiotherapy equipment. This study explores the absorption peak in the UV-visible (UV-vis) spectrophotometer as the relative intensity of polymerization. Theoretically, high intensity of polymerization results in high absorbance. The size of gold nanoparticles (GNPs) and dose of irradiation are expected to affect polymerization. Normoxic polymer gel samples using 2-Hydroxyethyl methacrylate (HEMA) as the monomer were prepared with different sizes of GNPs to study the effect of GNPs with ascorbic acid acting as the oxygen scavenger. Linear accelerator (LINAC) was the source of high irradiation x-ray energy as it is one of the most widely used radiotherapy equipment. The diagnostic x-ray unit acted as a low energy source. One crucial factor in fabricating the sample is the environment temperature. Radiation-induced polymer gel is environmentally sensitive where a low-temperature environment (<5◦C) is needed to ensure the structural stability of the gel. The UV-vis analysis shows that the absorbance increases when the irradiation doses increase, while the size of GNPs affects the absorbance value depending on the irradiation dose.

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