ConspectusX-ray luminescence is an optical phenomenon in which chemical compounds known as scintillators can emit short-wavelength light upon the excitation of X-ray photons. Since X-rays exhibit well-recognized advantages of deep penetration toward tissues and a minimal autofluorescence background in biological samples, X-ray luminescence has been increasingly becoming a promising optical tool for tackling the challenges in the fields of imaging, biosensing, and theragnostics. In recent years, the emergence of nanocrystal scintillators have further expanded the application scenarios of X-ray luminescence, such as high-resolution X-ray imaging, autofluorescence-free detection of biomarkers, and noninvasive phototherapy in deep tissues. Meanwhile, X-ray luminescence holds great promise in breaking the depth dependency of deep-seated lesion treatment and achieving synergistic radiotherapy with phototherapy.In this Account, we provide an overview of recent advances in developing advanced X-ray luminescence for applications in imaging, biosensing, theragnostics, and optogenetics neuromodulation. We first introduce solution-processed lead halide all-inorganic perovskite nanocrystal scintillators that are able to convert X-ray photons to multicolor X-ray luminescence. We have developed a perovskite nanoscintillator-based X-ray detector for high-resolution X-ray imaging of the internal structure of electronic circuits and biological samples. We further advanced the development of flexible X-ray luminescence imaging using solution-processable lanthanide-doped nanoscintillators featuring long-lived X-ray luminescence to image three-dimensional irregularly shaped objects. We also outline the general principles of high-contrast in vivo X-ray luminescence imaging which combines nanoscintillators with functional biomolecules such as aptamers, peptides, and antibodies. High-quality X-ray luminescence nanoprobes were engineered to achieve the high-sensitivity detection of various biomarkers, which enabled the avoidance of interference from the biological matrix autofluorescence and photon scattering. By marrying X-ray luminescence probes with stimuli-responsive materials, multifunctional theragnostic nanosystems were constructed for on-demand synergistic gas radiotherapy with excellent therapeutic effects. By taking advantage of the capability of X-rays to penetrate the skull, we also demonstrated the development of controllable, wireless optogenetic neuromodulation using X-ray luminescence probes while obviating damage from traditional optical fibers. Furthermore, we discussed in detail some challenges and future development of X-ray luminescence in terms of scintillator synthesis and surface modification, mechanism studies, and their other potential applications to provide useful guidance for further advancing the development of X-ray luminescence.

Advancing X-ray Luminescence for Imaging, Biosensing, and Theragnostics.

Time–temperature indicator (TTI) technologies allow for nondestructive and real‐time quality management of perishable products during the entire transport–storage process, which provides an important guarantee for the product safety of end users. However, the existing TTI technologies still have shortcomings in recyclability, sensitivity, and environmental tolerance, limiting their widespread applications. Herein, a new TTI route based on the light storage effect in persistent luminescent (PersL) materials is proposed. Such TTI is designed on account of the principle that the release rate of light‐induced trapped carriers in PersL materials is closely dependent on the storage time and temperature, enabling to establish a correlation between the number of residual carriers and the freshness of perishable products. Taking KZnF3:Mn2+ as a model material, the light‐storage‐based TTI technology shows excellent recyclability, reliability, and environmental stability. This work reveals great potentials of PersL phosphors as information recording materials in advanced TTI application and next‐generation biological detection technology.

Recyclable Time–Temperature Indicator Enabled by Light Storage in Particles

Solution-processed scintillators hold great promise in fabrication of low-cost X-ray detectors. However, state of the art of these scintillators is still challenging in their environmental toxicity and instability. In this study, we develop a class of tetradecagonal CuI microcrystals as highly stable, eco-friendly, and low-cost scintillators that exhibit intense radioluminescence under X-ray irradiation. The red broadband emission is attributed to the recombination of self-trapped excitons in CuI microcrystals. We demonstrate the incorporation of such CuI microscintillator into a flexible polymer to fabricate an X-ray detector for high-resolution imaging with a spatial resolution up to 20 line pairs per millimeter (lp mm−1), which enables sharp image effects by attaching the flexible imaging detectors onto curved object surfaces.

/pdf/high-resolution-flexible-x-ray-luminescence-imaging-enabled-3o5vlnqh.pdf

High-resolution flexible X-ray luminescence imaging enabled by eco-friendly CuI scintillators

Recently, metal halides (MH) flexible X‐ray detectors have attracted remarkable research interest owing to their great potential for non‐planar imaging, which can eliminate imaging ghosting caused by the misfit between the detector and the object. In this review, recent progress in flexible X‐ray detectors, including advanced optimized techniques of MH and novel flexible substrate structures, is summarized. In addition, the main photoelectric property characterizations are depicted along with their detailed physical meaning and analytical methods. To conclude, the existing vital gap between development status and commercial requirements and the corresponding optimization research directions is also covered.

Xiaokun Li

Papers

Flexible X-ray luminescence imaging enabled by cerium-sensitized nanoscintillators