Halogen‐bonding boosting the high performance X‐ray imaging of organic scintillators

Abstract

Organic scintillators with efficient X‐ray excited luminescence are essential for medical diagnostics and security screening. However, achieving excellent organic scintillation materials is challenging due to low X‐ray absorption coefficients and inferior radioluminescence (RL) intensity. Herein, supramolecular interactions are incorporated, particularly halogen bonding, into organic scintillators to enhance their radioluminescence properties. By introducing heavy atoms (X = Cl, Br, I) into 9,10‐bis(4‐pyridyl)anthracene (BPA), the formation of halogen bonding (BPA‐X) enhances their X‐ray absorption coefficient and restricts the molecular vibration and rotation, which boosts their RL intensity. The RL intensity of BPA‐Cl and BPA‐Br fluorochromes increased by over 2 and 6.3 times compared to BPA, respectively. Especially, BPA‐Br exhibits an ultrafast decay time of 8.25 ns and low detection limits of 25.95 ± 2.49 nGy s−1. The flexible film constructed with BPA‐Br exhibited excellent X‐ray imaging capabilities. Furthermore, this approach is also applicable to organic phosphors. The formation of halogen bonding in bromophenyl‐methylpyridinium iodide (PYI) led to a fourfold increase in RL intensity compared to bromophenyl‐methyl‐pyridinium (PY). It suggests that halogen bonding serves as a promising and effective molecular design strategy for the development of high‐performance organic scintillator materials, presenting new opportunities for their applications in radiology and security screening.

Mechanochemical Synthesis of Cuprous Complexes for X-ray Scintillation and Imaging

“…As the X-ray dose rate increases from 4.58 to 278 μGy s –1 (Table S2), both materials exhibit consistent spectra, and their maximum intensities show a linear increase with the X-ray dose rate (Figure d). The calculated detection limit for Cu-1 and Cu-2 are remarkably low at 223.0 and 49.7 nGy s –1 , , representing just 1/25 and 1/111 of the common X-ray diagnostic standard dose rate of 5.5 μGy s –1 . This significant reduction in detection limit is advantageous for applications in low-dose X-ray imaging .…”

“…33,34 Also, it is further supported by the calculated nonradiative transition rates (k nr ), 34 where the k nr values decreased from 6.61 × 10 4 s −1 in Cu-1 to 5.60 × 10 4 s −1 in Cu- 2, leading to a significant enhancement of the RL intensity for Cu-2 in the solid-state. 4,26,34,35 Due to the outstanding scintillation performance of Cu-2, we subsequently employed it in X-ray radiography. After blending Cu-2 powder milled using a grinder with UV adhesive, we fabricated a Cu-2 scintillator film (10 wt %, 5 cm × 5 cm, Figure 4a) with a thickness of 80 μm using a facile scraping coating method, followed by curing it under UV irradiation for 10 min (see Experimental Section).…”

“…As shown in Table S1 and Figure d,e, a unit cell of both Cu-1 and Cu-2 single crystals consists of two Cu­(I) coordination molecules and two acetonitrile molecules, with each pair of molecules exhibiting two I···H–C interactions at distances of 3.888 Å (Cu-1) and 3.857 Å (Cu-2), respectively. The shorter I···H–C interactions in Cu-2 may restrict molecular vibration, thereby constraining nonradiative transition pathways. , Furthermore, we employed CrystalExplorer software to analyze the Hirshfeld surfaces and the distribution of different intermolecular interactions by generating two-dimensional fingerprint plots of these crystals. , As illustrated in Figure S4 and the pie charts in Figure h,i, compared with Cu-1, which has contributions from H···others interactions (73.1%), C···others interactions (18.5%), and I···others interactions (3.9%), the replacement of PH-Br in Cu-2 results in a more diverse array of intermolecular interactions, including H···others interactions (77.3%), C···others interactions (18.8%), I···others interactions (3.5%), and Br···others (4.9%). These plentiful intermolecular interactions effectively constrain molecular vibration and rotation, consequently further suppressing the nonradiative transition process. , Also, it is further supported by the calculated nonradiative transition rates ( k nr ), where the k nr values decreased from 6.61 × 10 4 s –1 in Cu-1 to 5.60 × 10 4 s –1 in Cu-2, leading to a significant enhancement of the RL intensity for Cu-2 in the solid-state. ,,, …”

Amplified Circularly Polarized and X-ray-Excited Luminescence of Easily Separated Chiral Donor–Acceptor Binaphthalene Imides through a Conformation Locking Strategy

“…The successful activation of CPL properties by conformation locking encouraged us to explore another emerging function, i.e., X-ray excited luminescence, − which remains challenging for organic scintillators in terms of detection limit, scintillation lifetime, and photostability. , The XEL properties of (S)-C1 , C2 , C3 , and C6 and (S)-open single crystals were measured under an X-ray source, whose XEL spectra exhibited similar profiles in contrast to their PL spectra (Figures S10 and S11). Compared with (S)-open , all of the locked imides gave stronger XEL intensities, while (S)-C1 showed almost 30-fold amplification.…”

Through‐Space Charge‐Transfer Organogold(III) Complexes Enable High‐Performance X‐ray Scintillation and Imaging

“…[9] Alternatively, organic materials are appealing X-ray scintillators, in virtue of their abundant resources, low cost, excellent mechanical flexibility, easy processing, and large-area depolyment. [10][11][12] Albeit the first demonstration of anthracene as an X-ray scintillator in 1979, the development of organic scintillators is mainly limited by their weak X-ray absorption and inefficient triplet exciton utilization. [13][14][15] Figure 1 schematically shows the X-ray absorption and conversion process between X-ray and organic scintillators.…”