Scintillation Liquids Loaded with Hafnium Oxide Nanoparticles for Spectral Resolution of γ Rays

Current mainstream spectroscopic scintillators for the detection of high-energy radiation are based on inorganic crystals and ceramics, which are difficult to scale up. Efforts have been made to synthesize plastic nanocomposite scintillators, though the resulting light yield is rather low, leading to low photopeak intensity and poor energy resolution. Here, a scintillating liquid containing HfO2 nanoparticles for increasing sensitivity to high-energy photons is demonstrated, with the addition of 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) as a primary dye and 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP) as a secondary dye. Naphthalene is used as a cosolvent for toluene to dissolve these functional components. The liquid scintillator retains a high transparency in the emission wavelength range, achieving a transmittance of up to 80% at nanoparticle loadings as high as 50 wt %. The use of the naphthalene cosolvent increases the light yield by 40%. The 137Cs γ photopeak is measured from the liquid scintillator containing 20 wt % HfO2 nanoparticles, with a deconvoluted photopeak energy resolution of 4.8%, which is better than that obtained from the conventional NaI(Tl) crystal scintillator.