Development of PVK-Based Plastic Scintillators Loaded with Bi2O3 Nanoparticles

We developed surface-modified Bi
2
O
3
nanoparticle-loaded plastic scintillators for application in scintillation detectors that have fast response to high-energy X-rays. As the host polymer, poly(9-vinylcarbazole) (PVK) was selected because PVK has a band gap of 3.5 eV, smaller than that of polystyrene (5.4 eV). The scintillation properties of the plastic scintillators with different concentrations of nanoparticles and phosphor (9,10-diphenylantrazene (DPA)) were characterized to optimize concentrations of nanoparticles and DPA. Nanoparticles of 4.5 ± 0.92 nm with high dispersibility in PVK matrix were successfully synthesized by subcritical hydrothermal synthesis. In the X-ray-excited radioluminescence (XRL) spectra, an emission peak around 440 nm was observed in all the samples as well as in the PL emission spectra. The scintillation light yields of the samples were estimated on the basis of the pulse height spectra for 67.41-keV X-rays. Detection efficiencies and light yields significantly larer than those of EJ-256 were achieved for all samples with a nanoparticle concentration of 10 wt%. Among them, the sample with Bi
2
O
3
nanoparticle concentration of 10 wt% and DPA concentration of 0.25 mol% showed the highest light yield of 10000 photons/MeV for high-energy X-rays of 67.41 keV. Decay time constants of about 6-18 ns were obtained for all samples regardless of nanoparticle concentration. We achieved the fabrication of plastic scintillators with high light yield and high detection efficiency without losing the fast response derived from plastic scintillators.