Halogen-bonded charge-transfer co-crystal scintillators for high-resolution X-ray imaging

Area of Science:

• Materials Science
• Organic Chemistry
• Solid-State Physics
• Radiological Imaging

Background:

• Organic scintillators often suffer from poor X-ray absorption due to low atomic number elements.
• Co-crystal engineering with halogen-containing molecules offers a promising strategy to enhance scintillator performance.
• Developing efficient organic scintillators is crucial for advanced X-ray detection and imaging.

Purpose of the Study:

• To synthesize a novel fluorescent dye, 2,5-di(4-pyridyl)thiazolo[5,4-d]thiazole (Py2TTz).
• To engineer co-crystals of Py2TTz with halogenated compounds (I2F4B, I3F3B) to improve X-ray absorption and scintillation properties.
• To investigate the mechanism behind the enhanced performance, focusing on halogen bonding and its impact on photophysical properties.

Main Methods:

• Synthesis of the fluorescent dye Py2TTz.
• Co-crystallization of Py2TTz with 1,4-diiodotetrafluorobenzene (I2F4B) and 1,3,5-trifluoro-2,4,6-triiodobenzene (I3F3B).
• Characterization of scintillation properties (decay time, luminescence intensity, detection limit) and spatial resolution.
• Theoretical calculations and single-crystal structure analysis to elucidate the role of halogen bonding.

Main Results:

• The co-crystal Py2TTz-I2F4 exhibited exceptional scintillation properties: ultrafast decay time (1.426 ns), 146% higher luminescence intensity than Bi3Ge4O12, and a low detection limit (70.49 nGy s⁻¹).
• Halogen bonding between I2F4B and Py2TTz was identified as the key factor, promoting charge transfer and reducing non-radiative decay.
• A flexible X-ray film based on Py2TTz-I2F4 achieved an ultrahigh spatial resolution of 26.8 lp/mm.

Conclusions:

• Co-crystal engineering using halogen bonding is a highly effective strategy for developing high-performance organic scintillators.
• The Py2TTz-I2F4 co-crystal demonstrates superior X-ray detection capabilities and spatial resolution for advanced imaging applications.
• This approach significantly enhances X-ray absorption, material conductivity, and fluorescence quantum yield, overcoming limitations of traditional organic scintillators.