Search

Precise detection of low-dose X- and γ-radiations remains a challenge and is particularly important for studying biological effects under low-dose ionizing radiation, safety control in medical radiation treatment, survey of environmental radiation background, and monitoring cosmic radiations. We report here a photoluminescent uranium organic framework, whose photoluminescence intensity can be accurately correlated with the exposure dose of X- or γ-radiations. This allows for precise and instant detection of ionizing radiations down to the level of 10 -4  Gy, representing a significant improvement on the detection limit of approximately two orders of magnitude, compared to other chemical dosimeters reported up to now. The electron paramagnetic resonance analysis suggests that with the exposure to radiations, the carbonyl double bonds break affording oxo-radicals that can be stabilized within the conjugated uranium oxalate-carboxylate sheet. This gives rise to a substantially enhanced equatorial bonding of the uranyl(VI) ions as elucidated by the single-crystal structure of the γ-ray irradiated material, and subsequently leads to a very effective photoluminescence quenching through phonon-assisted relaxation. The quenched sample can be easily recovered by heating, enabling recycled detection for multiple runs., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Scintillators are a unique class of luminescent materials with specific applications towards radiation detection. The emitters within state‐of‐the‐art scintillators are mostly limited to bismuth, cerium, europium, thallium, lead, tungsten, etc. A shared feature of these elements is the relatively high atomic number, which is responsible for high radiation stopping power and radiation‐induced luminescence. Searching for new scintillating materials is an essential target aiming at specific applications. In this Concept article, we will discuss our recent works on the topic of "uranyl‐bearing scintillators". As a virgin territory in this field, uranyl‐bearing scintillators show intrinsic merits for designing new materials with X‐ray detection capability, that is, the large photoelectric cross‐section, high X‐ray attenuation efficiency, and high crystal density. In addition, we also present challenges in the further development of the uranyl‐bearing scintillators. [ABSTRACT FROM AUTHOR]

Abstract: The combination of high atomic number and high oxidation state in UVI materials gives rise to both high X‐ray attenuation efficiency and intense green luminescence originating from ligand‐to‐metal charge transfer. These two features suggest that UVI materials might act as superior X‐ray scintillators, but this postulate has remained substantially untested. Now the first observation of intense X‐ray scintillation in a uranyl–organic framework (SCU‐9) that is observable by the naked eye is reported. Combining the advantage in minimizing the non‐radiative relaxation during the X‐ray excitation process over those of inorganic salts of uranium, SCU‐9 exhibits a very efficient X‐ray to green light luminescence conversion. The luminescence intensity shows an essentially linear correlation with the received X‐ray intensity, and is comparable with that of commercially available CsI:Tl. SCU‐9 possesses an improved X‐ray attenuation efficiency (E>20 keV) as well as enhanced radiation resistance and decreased hygroscopy compared to CsI:Tl. [ABSTRACT FROM AUTHOR]

Keywords: luminescence; radiation detection; scintillators; uranium As a new area in this field, uranyl-bearing scintillators show intrinsic merits for designing new materials with X-ray detection capability, that is, a large photoelectric cross-section, high X-ray attenuation efficiency, and high crystal density. Luminescence, radiation detection, scintillators, uranium. [Extracted from the article]