Highly Luminous Scintillating Nanocomposites Enable Ultrafast Time Coincidence Resolution for γ-rays Detection with Heterostructured Multilayer Scintillators

Abstract

Brighter fast scintillators are needed for advanced applications to acquire data with high signal-to-noise ratio in short time windows, like in the time-of-flight positron emission tomography (ToF-PET) imaging technique for cancer. A new composite polymeric fast scintillator loaded with high-density hafnium dioxide (HfO2, hafnia) nanoparticles is developed here to be used for detection of the 511 keV γ-rays employed in ToF-PET. By a fine tuning and engineering of the electronic properties of its components, namely the polymeric matrix, the dense nanoparticles and the embedded fluorescent dye, a highly luminous polymeric scintillating nanocomposite is realized, showing an unprecedented scintillation efficiency for plastic materials and nanosecond-scaled scintillation decay. Nanocomposite films are then coupled to dense bismuth germanate (Bi4Ge3O12, BGO) crystal sheets to fabricate an heterostructured multilayer scintillator as a prototype pixel for ToF-PET scanners. Thanks to the nanocomposite high scintillation efficiency, the prototype detector shows an ultrafast time resolution of 115 ps for 511 keV γ-rays detection, actually limited by the non-optimal light transport properties in the pixel and by the sensitivity of the employed photodetector.