A Review on X-ray Detection Using Nanomaterials

Background: Since the discovery of X-rays by Röntgen in 1895, X-rays have been widely applied in multiple disciplines and industries. Since the X-rays are well beyond human visibility, materials are used for the high-energy X-ray detections. This review focuses on the X-ray detection using nanomaterials. Methods: X-rays can be detected by (1) X-ray films, which is a traditional method for imaging; (2) phosphor- or scintillator-based detectors, which are used as an indirect detection method to convert the X-rays into visible lights; (3) semiconductor-based detectors, which are used as a direct detection method for X-ray imaging and X-ray exposure measurements; and (4) gas detectors, which are used for X-ray exposure measurements. Results: Materials for X-ray detection were summarized, including phosphors, scintillators, and semiconductors. Their characteristic properties were compared. Nano size effects on the X-ray detection were discussed. X-rays can be detected using random nanomaterials (nanoparticles, nanofibers and nanowires, nanocomposites). The scintillator and phosphor nanoparticles were found to exhibit enhanced luminescence and shortened decay time, while luminescence suppression was also observed. Assembly of a core/shell structure was suggested as a strategy to increase such luminescence intensity. Nanofibers and nanowires have been prepared for improved spatial resolution. Since it is expensive and also technically challenging to grow high-quality single crystal scintillators, alternative ways have been developed to fabricate nanocomposites with scintillator or phosphor nanoparticles that demonstrated high performance. For X-ray imaging, it is preferable to vertically align scintillator material to reduce light cross scattering and to achieve higher spatial resolution; ideally by confining the scintillator inside of walls with light guides. Finally, scintillators have been made in nanochannels for improved spatial resolution and light output. Conclusion: The application of nanomaterials for X-ray detection is limited when compared to other applications using nanomaterials. The research on X-ray detection using nanomaterials is an open field for conducting studies of excitation mechanisms, exploration of new scintillator materials, and applications of active compounds.