Poly(vinyl alcohol) film containing methyl viologen as a highly sensitive dosimeter

Color development of polymer films containing methyl viologen (MV2+) as an electron acceptor by gamma- or electron-beam irradiation was studied. The ionizing radiation induced one-electron reduction of MV2+ to produce the intensely blue-colored cation radical (MV+radical) in the polymer film. Poly(vinyl alcohol) (PVA) was an excellent matrix for the MV+radical formation, leading to the greatest G(MV+radical) value of 9.8 among the polymers studied. The hydroxy groups of not only polymeric alcohol, PVA, but also monomeric alcohols added to poly(vinyl acetate) film were effective for promotion of the radiolytic one-electron reduction of MV2+. The G(MV+radical) value obtained by gamma-irradiation of the MV2+-PVA film was enhanced from 9.8 top 12.7 by the addition of sodium formate or potassium formate. The MV+ radical formed by ionizing radiation in the PVA matrix was extremely stable even when exposed to air. The MV2+-PVA film is useful for a highly sensitive dosimeter in the lower dose range below 10 krad. (author)