Facile Single-Precursor Synthesis and Surface Modification of Hafnium Oxide Nanoparticles for Nanocomposite γ-Ray Scintillators

Inorganic nanoparticles/polymer nanocomposites provide a low cost, high performance alternative for gamma scintillation. However, inorganic nanoparticles used thus far suffer from either moderate atomic numbers or low band gaps, limiting the gamma stopping power and photoelectron production in these systems. Here, a highly efficient, facile single-precursor synthesis protocol is reported for hafnium oxide nanoparticles with an average diameter of 5 nm. The nanoparticle surface is further functionalized for the fabrication of highly transparent bulk-size nanocomposite monoliths (2 mm thick, transmittance at 550 nm >75%) with nanoparticle loadings up to 40 wt% (net hafnium wt% up to 28.5%). Using poly(vinyltoluene) as the matrix, 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole and 1,4-bis(5-phenyl-2-oxazolyl)benzene as the cascade fluors, and hafnium oxide nanoparticles as the gamma sensitizer, the nanocomposite monolith of 1 cm diameter and 2 mm thickness is fabricated capable of producing a full energy photopeak for 662 keV gamma rays, with the best deconvoluted photopeak energy resolution <8%. An efficient multigram-scale single-precursor synthesis of high-quality hafnium oxide nanoparticles is reported. After surface modification, these nanoparticles are used to fabricate highly transparent nanocomposite monoliths (2 mm thick, T_{550 nm} > 75%) at loadings up to 40 wt%. The nanocomposite monoliths are efficient in detecting gamma radiation, being capable of producing a full energy photopeak with deconvoluted resolution <8%.