High-Z Nanocomposites for Fast and Radiation Hard Scintillation

Low-cost, high-density Gamma ray plastic scintillators with fast decay and high light yield superior to inorganic scintillators and semiconductor detectors are highly needed in the fields of nuclear physics, national security, border control, along with various medical and industrial sectors. Chemelectronics LLC will team up with the University of California, Los Angeles to development and commercialization of nanocomposite monoliths comprising high-Z nanoparticles for gamma-ray spectroscopy in portal monitors. These nanocomposites retain high optical transparency at nanoparticles loadings up to 60 wt%. Measured scintillation light yields are much higher than plastic scintillators loaded with high-Z organo-metallic compounds, with nanosecond decay time. The composition and synthetic chemical of the polymer matrix will also be investigated to enhance the light yield and scalability at low cost (expected to be 1000 cm3 ) to meet the performance metrics required for radiation portal monitors. During the Phase I study, the team modified the synthesis and functionalization of the synthesis of HfO2 nanoparticles and obtained nanocomposites containing up to 40 wt% HfO2 nanoparticles with emission weighted longitudinal transmittance (EWLT) of 79.5%. A new conjugated organic compound, 9,9-dimethyl-9H-fluorene (MF), was used to augment PVT and improved the gamma pulse light yield by 11%. The nanocomposite scintillator ((thickness=2 mm; diameter =17 mm)) containing 40% wt% HfO2 nanoparticles and 20 wt% MF produced a prominent Cs-137 gamma photopeak with deconvoluted photopeak energy resolution of 7.2% and successfully scaled up to 2.7 cm3 volume. Nanocomposites loaded with luminescent quantum dots, CZS quantum dots and perovskite CsPbBr3 QDs, were also synthesized. Phase II of the project will iterate the synthesis of nanocomposite scintillators capable of gamma-ray spectroscopy. The gamma-ray photopeak is obtained by loading high-Z nanoparticles while retaining the high optical transmittance, high light yield, and fast scintillation decay of unloaded plastic scintillators. The synthetic chemistry will be developed, such that low-cost raw chemicals and lowcost scalable fabrication processes can be employed, in order to ease the transition into production for wide deployment in RPMs. The technical objective is to further improve the composition and synthesis protocol developed in Phase I, targeting the performance metrics of solid-state nanocomposite scintillators with volume ~20 cm3 and ~10% photopeak energy resolution for 662 keV gamma. The new scintillators will outperform existing plastic scintillators in RPMs by providing spectroscopic identification of radioactive sources on site and in situ. Furthermore, the nanocomposite scintillators will provide advanced solutions for the measurement needs of high energy particles at the nation’s nuclear facilities and for nuclear physics studies. The nanocomposite scintillators offer the unique combination of comparable light yield, ns-scale time resolution, and low cost of unloaded plastic scintillators, but twice the density and 5-10 times higher effective Z. The low-cost nanocomposite scintillator could solve financial challenges for both healthcare providers and patients to process radiation diagnosis, screening and treatment at lower costs as well.