X-ray detection at an ultralow level

Researchers from the King Abdullah University of Science and Technology (KAUST) have succeeded in producing an efficient, robust and flexible scintillation film to bring significant improvements in medical, industrial and security X-ray imaging. Their breakthrough has been published in the journal ACS Energy Letters.

Scintillation materials release visible light, or ‘scintillate’, in response to absorbing invisible X-ray high-energy photons. They are used to construct digital images that reveal the relative passage and obstruction of X-rays as they encounter any solid object, such as a region of the body, an industrial component or an object being screened for security purposes. X-ray scintillation is already routine technology, but researchers are continually exploring ways to make it more sensitive, efficient and readily adaptable.

“Currently, used materials suffer from several drawbacks, including complex and high-cost fabrication processes, radioluminescence afterglow and non-tuneable scintillation,” said Yang Zhou, a postdoc researcher at KAUST.

Materials called lead halide perovskites have attracted considerable attention and shown significant promise. Novel perovskites are a category of materials that share the same crystal structure as the natural perovskite mineral calcium titanium oxide, but they include a variety of different atoms that replace all or some of those found in natural perovskite. Lead halide perovskites incorporate both lead and one or more elements of the halogen group, such as fluorine, chlorine, bromine and iodine.

Despite the abilities of lead halide perovskites as X-ray scintillators, their commercial applications are limited by technical problems, including poor stability when exposed to light and air, reabsorption of some of the scintillated light and the toxicity of lead. The KAUST team overcame these problems by developing lead-free metal halides based on cesium, copper and iodide ions in the ratio Cs₃Cu₂I₅, with crystals of that material incorporated into thin and flexible films of the polymer polydimethylsiloxane.

The researchers say it was challenging to get the copper halide powders uniformly distributed in the film, but they eventually achieved this by dispersing the powder in solvent before adding polydimethylsiloxane. Their resulting scintillation screens have the ability to detect X-rays at ultralow levels — approximately 113 times lower than a typical standard dose for X-ray medical imaging — while the X-ray spatial resolution achieved in their study is the highest reported to date for powder-based screens.

“The physical flexibility of our films is also very important,” said Omar Mohammed, leader of the research group. He explained that highly efficient flexible scintillation screens are urgently needed for using X-rays to better analyse awkward shapes.

The team already has plans to commercialise their advance. They also hope to refine their fabrication techniques and explore the potential of similar screens made from similar material compositions.

Image caption: The new scintillation material can bring significant improvements to X-ray imaging in medicine, industry and security. Image ©2022 KAUST.

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