Abstract
Gamma sensitive plastic scintillators are of critical importance in the fields of nuclear nonproliferation, medical imaging, and high energy physics. However, there is often a trade-off between high light yield and high loading of high-Z components, both of which play an essential role in gamma ray detection. This work takes advantage of triplet exciton harvesting to increase gamma light yield by utilizing 1,3-di(9H-carbazol-9-yl)benzene and 9,9-dimethyl-9H-fluorene as triplet hosts to facilitate Dexter energy transfer to bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrPic), a blue light emitting phosphorescent dye. A plastic scintillator containing 20 wt % MF, 10 wt % mCP, and 2 wt % FIrPic has a high gamma light yield of 14 800 Ph/MeV. Incorporating 20-35 wt % hafnium oxide nanoparticles into this organic matrix results in nanocomposites that demonstrate a gamma photopeak energy resolution of 6.4-9.7% at 662 keV while still retaining a high gamma light yield between 8800 and 10 800 Ph/MeV.