We developed plastic scintillators loaded with perovskite quantum dots (QDs) to enhance the detection efficiency for high-energy photons such as X-rays and gamma rays. QDs with different emission wavelengths were loaded onto plastic scintillators at 5 wt%. The emission from the QDs only was observed in the radioluminescence spectra under X-ray irradiation. The photoluminescence decay behavior indicates that the absorption of the QD emission by the QDs themselves (self-absorption) results in long decay components, which were also observed in the scintillation decay. The detection efficiency for 67.4 keV X-rays was successfully enhanced by loading, although the scintillation light yield was reduced.

In this study, zirconium acetylacetonate (Zr(acac) 4 ) containing the isotope 96 Zr was studied as a liquid scintillator for the possible detection of neutrinoless double beta decay. To avoid the absorption of scintillation by ligand absorption, the phosphor Coumarin 7 was assessed as a green-emitting liquid scintillator. By dissolving 3 g/L of Coumarin 7 in anisole, a liquid scintillator with a light yield of 12000 photons/MeV was fabricated. Subsequently, the liquid scintillator was loaded with Zr(acac) 4 . In the liquid scintillator containing 10 wt% Zr(acac) 4 , the light yield of scintillation was 370 photons/MeV for a blue-emitting liquid scintillator, while a light yield of 1900 photons/MeV was determined for a green-emitting liquid scintillator. The scintillation decay time constants of the fast component were around 4.4 ns. Liquid scintillators with a high light yield that avoid absorption by Zr(acac) 4 can be prepared using Coumarin 7.

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The observation of neutrinoless double beta decay is an important issue in nuclear and particle physics. The development of organic liquid scintillators with high transparency and a high concentration of the target isotope would be very useful for neutrinoless double beta decay experiments. Therefore, we propose a liquid scintillator loaded with metal oxide nanoparticles containing the target isotope. In this work, 6-phenylhexanoic acid-modified ZrO2 nanoparticles, which contain 96Zr as the target isotope, were synthesized under sub/supercritical hydrothermal conditions. The effects of the synthesis temperature on the formation and surface modification of the nanoparticles were investigated. Performing the synthesis at 250 and 300 °C resulted in the formation of nanoparticles with smaller particle sizes and higher surface modification densities than those prepared at 350 and 400 °C. The highest modification density (3.1 ± 0.2 molecules/nm2) and Zr concentration of (0.33 ± 0.04 wt.%) were obtained at 300 °C. The surface-modified ZrO2 nanoparticles were dispersed in a toluene-based liquid scintillator. The liquid scintillator was transparent to the scintillation wavelength, and a clear scintillation peak was confirmed by X-ray-induced radioluminescence spectroscopy. In conclusion, 6-phenylhexanoic acid-modified ZrO2 nanoparticles synthesized at 300 °C are suitable for loading in liquid scintillators.

Bi-loaded PVK-based plastic scintillators doped with bis-MSB are applicable for high counting-rate measurement of high-energy X-rays. They showed a higher detection efficiency and light yield than EJ-256 under 67.41 keV X-ray irradiation.