X-rays are electromagnetic waves with short wavelengths and strong penetrability in physical matter, including live organisms. Scintillators capable of converting X-rays into the ultraviolet (UV), visible or near-infrared (NIR) photons are widely employed to realize indirect X-ray detection and XEOL imaging in many fields. They include medical diagnosis, computed tomography (CT), space exploration, and non-destructive industrial material and security inspections.

Commercial bulk scintillators possess high light yield (LY) and superior energy resolution. However, they suffer from serval drawbacks, i.e., complex fabrication procedures, expensive experimental equipment, non-tunable XEOL wavelength and poor device processability. They all produce emissions in the visible spectral range, but having XEOL in the NIR range may find more interesting applications in biomedicine. Thick crystals also generate light scattering followed by evident signal crosstalk in a photodiode array.

Recently, metal halide perovskites have been investigated for X-ray detection. Unfortunately, these materials also exhibited some intrinsic limitations, such as poor photo-/environmental- stability, heavy metal toxicity and low LY. Thus, the search for developing a new generation of scintillators is still a considerable focus of scientific research.
In a new paper published in eLight, a team of scientists, led by Professor Prasad N. Paras from the University of Buffalo, investigated the use of lanthanide-doped fluoride NSs. Their paper, "Next Generation Lanthanide Doped Nanoscintillators and Photon Converters," looked at design strategies and nanostructures that allow manipulation of excitation dynamics in a core-shell geometry.

Lanthanide-doped fluoride NSs avoid the limitations of bulk scintillators and metal halide perovskites. They also exhibit many useful properties. The core-shell structures of the lanthanide doped fluoride NSs can be tuned and designed on demand by employing a cheap and convenient wet-chemical method. The emission wavelengths can be tuned and extended to the second NIR window, benefiting from the abundant energy levels of lanthanide activators.

These NSs show superior photostability, low toxicity and convenient device processability. It makes them promising candidates for next-generation NSs and XEOL imaging. Moreover, they exhibit XEPL property, showing promising applications in biomedicine and optical information encoding. The combination of XEOL and XEPL makes them suitable for broadening the scope of their applications.

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