Photoluminescent properties of BaF2 scintillator-polystyrene composite films under vacuum ultraviolet radiation

This work reports a new synergistic effect observed in self-sustainable composite films, composed by barium fluoride (BaF₂) nanoparticles embedded in polystyrene matrix. Optical absorption measurements were performed in the ultraviolet and visible range. The luminescent properties were investigated by photoluminescence (PL) under excitation in the vacuum ultraviolet region. The PL results showed that self-trapped excitons of BaF₂ nanoparticles incorporated into the polymeric matrix are excited at 5.6 eV. This value is 3.4 eV lower than the typical exciton formation energy observed for BaF₂ isolated nanoparticles. This phenomenon can be understood as result of a synergistic effect, between polystyrene and BaF₂, involving antenna effect and Foster energy transfer. PL lifetime measurements showed that the decay is composed by two main process with short lifetime. From chromatic coordinates of the emitted light it was possible to observe that light emission can be tuned to different shades of colors between blue and green.