Fast neutron detection is significant for neutron imaging and flux monitoring but cannot be directly achieved by inorganic semiconductors. The traditional detection is mainly mediated by an organic scintillator and a coupled photodetector, resulting in signal losses. Here, a direct detection method for fast neutrons is demonstrated based on organic semiconducting single crystals (OSSCs) detectors. Methyl 4-hydroxybenzoate (4MHB, C 6 H 5 O-COOCH 3 ) and 4-hydroxycyanobenzene (4HCB, C 6 H 5 O-CN). The organic semiconductor acts as a fast neutron sensitive material due to its high hydrogen density, simultaneously as a semiconductor that generates the electric signal. The detectors based on 4MHB crystals can quantitatively measure the dose and energy of the fast neutron flux with a response time of 0.5 µs and detection efficiency of 78.5% cm −3 . Effects of functional groups on fast neutron detection performances are also investigated as a guideline to synthesis new molecules for this purpose. Furthermore, neutron radiation effects on these detectors are investigated. Hydrogen-related point defects are generated by fast neutrons, but device performances remain robust after irradiation of 10 13 n cm −2 fast neutrons. This study demonstrates that OSSCs show great potential as direct fast neutron detectors and particularly have highly-localized and tissue-equivalent properties that benefit neutron imaging and cancer therapy applications.
Metal-organic frameworks (MOFs) glass is a newly invented hybrid materials with the unique optical response and great potential for photonic applications. Unfortunately, limited by the high viscosity and instability issue of the ZIF-62 precursor, the controllable synthesis of homogeneous MOFs glass remains a significant challenge. In this manuscript, it is found that reducing the stoichiometric ratio between Zn ions and the ligand precursor can effectively suppress the growth of the ZIF-62 and enable to obtain tiny precursor particles. By using them, the homogenous MOFs glass free of bubbles can be fabricated by gentle heat-treatment. This hybrid MOFs glass exhibits interesting optical response, including intense luminescence, atmosphere sensitive optical response and high energy particle scintillating emission. The applications for active atmosphere sensing and neutron detection with extremely high signal-to-noise ratio of 27.1 dB are demonstrated. The results suggest that homogenous amorphization of MOFs may create a new type of photonic material with unprecedent optical response and significant sensing application.
Jinqing Liang,Chao Li,Qi Wu,Lu Yao,Yang Hai,Xunsheng Zhou,Cai Lin Wang
Inorganic micro- or nanocrystal/polymer composite scintillators have been widely used in X-ray and neutron detection, but most of them are unable to satisfy the requirements of multiple detections at the same time owing to the limited absorption cross-sections of radiations. Here, we report bright, single-phase Ce-doped LiYSiO4 with a photoluminescence quantum yield (PLQY) of 68% by optimizing raw material ratios and doping concentrations. The electronic structures and traps were investigated by calculations based on density functional theory (DFT) methods and optical experiments. Further, transparent Ce-doped LiYSiO4/polydimethylsiloxane (PDMS) composite scintillators have been obtained by optimizing preparation processes, and their applications for X-ray imaging and thermal neutron detection have been demonstrated. The results show that the composite scintillator achieves a resolution of 7 line pairs per millimeter (lp/mm) at a modulation transfer function (MTF) for 0.2 under X-ray irradiation. The light yield under thermal neutron irradiation is 4000 photons/thermal neutron, and the pulse decay curves consist of two fast-decaying components of 4 and 48 ns. The neutron-gamma events were discriminated by a pulse gradient analysis (PGA) method with a figure of merit (FOM) of 1.53. The transparent, flexible, and fast-decaying composite scintillators developed in this work may be used for multimodal radiation detection.
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