Quantum materials could be the future of high-energy X-ray imaging and particle detection

A scintillator is a detector that visualizes high-energy X-rays or particles with a flash of light, forming an image. Its many applications include particle physics, medical imaging, X-ray security, and more.

However, despite their usefulness, scintillators pose a challenge to researchers. Until recently, scientists had to decide whether fast imaging or optimal performance was more important when choosing the appropriate scintillator technology for a particular experiment.

Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory may have found a solution to this dilemma. This includes scintillator materials made up of spherical particles that are 20 billionths of a meter in size. The study is published in the journal Nature Communications.

Although these nanoparticles are incredibly small, they have a complex structure consisting of a ball-shaped core of cadmium sulfide surrounded by a thin shell of cadmium selenide and a thick shell of cadmium sulfide. Scientists from the Department of Energy’s Oak Ridge National Laboratory, Bowling Green State University (BGSU), and Northwestern University collaborated on the project.

Due to quantum mechanical effects, these nanoparticles have valuable optical and electronic properties not possible with larger particles. BGSU scientists synthesized these nanoparticles, called quantum shells, to form the dense lattices that make up the scintillator material.

This applies to ultrafast radiation detection as well as the high-resolution imaging possible with X-ray sources such as the Advanced Photon Source (APS) at Argonne, a DOE Office of Science user facility.

Everyday applications of scintillator technology are found in dental clinics. An X-ray beam is directed through the patient’s mouth onto a film of reactive material, which burns an image of the teeth for the dentist to check for potential defects.

While this type of imaging is useful for dentists and doctors performing chest X-rays, it does not have the power or precision required for nanoscale imaging such as that performed by APS. It requires scintillator materials that are efficient, fast-responsive, have high spatial resolution, durable, and scalable to large sizes.

The quantum shell recently developed by the research team meets these criteria. “Quantum shells may be suitable for imaging in dental clinics, but they are much less useful for scintillators in light sources like APS, or for X-ray imaging of engines running with liquid inside. It is suitable,” said Burak Guzelturk. , a physicist in Argonne’s X-ray science department.

“Traditional scintillators emit light when excited by an X-ray beam, and they have a unique lifetime,” said Benjamin Diroll, a scientist at the Center for Nanoscale Materials, a Department of Energy Office of Science User Facility at Argonne. said.

“Some of them are hundreds of nanoseconds, or even microseconds. Quantum shell scintillators achieve single-digit nanosecond lifetimes while maintaining efficiency levels comparable to conventional scintillators.”

Guzelturk compared quantum shells to another similar light-emitting material, quantum dots. “In quantum dots, the emission usually comes from the central part of the nano-object, and the color of the emitted light depends on its size. On the other hand, in quantum shells, the emission does not come from the central part of the nano-object; it is the core. but are actually adjacent shells within the nanoparticle.”

The thickness of that shell determines how light is emitted. Scintillator materials generated from quantum shells provide fast, clear imaging and long-term durability.

Classic scintillators tend to be very thick. As a result, it can shine in the front, back, or center and tends to blur the desired image. Quantum shell scintillators can be fabricated as thin films on substrate materials, thus circumventing this problem.

“Commercial scintillators made of lightweight elements need to be a few millimeters thick,” Guzelturk explained. “In our case, we realized that we could make the quantum shell scintillator much thinner, only a few micrometers, while still achieving both strong X-ray absorption and high spatial resolution imaging.”

The advent of quantum shell scintillators for high-resolution and ultrafast imaging has allowed scientists to circumvent the limitations of traditional scintillator technology. This pioneering work shows the amazing potential of these nanoscale quantum materials. By exploiting its unique optical and electronic properties, researchers can break new ground in fields ranging from particle physics to medical diagnostics.