Sensitized Triplet-Triplet Anihilation in Nanostructured Polymeric Scintillators Allows for γ/neutrons Pulse Shape Discrimination

Scintillation counters are an important family of radiation detectors that record the photon emission of scintillating materials in response to incident radiation. They are widely used in high-energy physics experiments, nuclear threat detection and power plants and medical dosimetry.<br/>Organic liquid and plastic scintillators can not only identify, but also distinguish high-energy neutrons and charged particles from gamma-radiation background by exploiting the pulse shape discrimination (PSD). The PSD technique consists of a time-gated analysis of the transient voltage pulses generated in the photodetector of the scintillation counter. This analysis allows to assess the relative intensities of the fast and slow components of the scintillation signals, i.e., prompt and delayed emission, which in turn depend on the nature of the incident radiation and therefore constitute the base of the discrimination process.<br/>However, achieving efficient PSD with plastic scintillators, which are attractive due to their mechanical robustness, economic effectiveness, and manufacturability compared to liquid or crystalline scintillators, has proved to be challenging. This study demonstrates that is possible to perform PSD, discriminating α-particles and neutrons from γ-rays with a time response that is better than that of commercial scintillators by exploiting nanostructured polymeric scintillators. These scintillators can be synthesized under ambient conditions in a one-pot procedure and are made of a cross-linked solid polymer matrix in which non-polar liquid nanodomains are embedded. These nanodroplets contain a triplet-triplet annihilation (TTA) active scintillating dye [1-2] and enable efficient, localized bimolecular energy transfer processes that are typically hard to achieve in solid polymers. Moreover, the liquid like molecular dynamics in the nanodroplets facilitates the energy transfer process and allows the solubilization of triplet sensitizer that is difficult to include in solids.<br/>We show that the incorporation of this triplet sensitizer, even at ultra-low concentration, further enhances the sensitivity and discrimination ability of the scintillator compared to its non-sensitized counterparts [3].<br/>The proposed material platform has an unprecedented compositional versatility in comparison to alternative plastic scintillator designs, in particular with respect to the choice of the dye pairs that can be embedded. Furthermore, the TTA efficiency reached thanks to this design is impossible to achieve in conventional bulk amorphous plastic scintillators. Consequently, we anticipate that this easy-to-handle material platform will spark future developments of high-tech ultrasensitive detectors that enable the efficient and fast radiation/particles discrimination and detection of rare, low-energetic events.<br/><br/><br/>1. Vadrucci, R. et al. Nanodroplet containing polymers for efficient low power light upconversion. Advanced Materials 29, 1702992 (2017)<br/>2. Saenz, F. et al. Nanostructured Polymers Enable Stable and Efficient Low Power Photon Upconversion. Advanced Functional Materials 31, 2004495 (2021)<br/>3. Hu at al. Sensitized Triplet–Triplet Annihilation in Nanostructured Polymeric Scintillators Allows for Pulse Shape Discrimination, Advanced Materials 2400443 (2024)