Next generation lanthanide doped nanoscintillators and photon converters

Scintillators are of significance for the realization of indirect X-ray detection and X-ray excited optical luminescence (XEOL) imaging. However, commercial bulk scintillators not only require complex fabrication procedures, but also exhibit non-tunable XEOL wavelength and poor device processability. Moreover, thick crystals usually generate light scattering followed by evident signal crosstalk in a photodiode array. Lanthanide doped fluoride nanoscintillators (NSs) prepared with low-temperature wet-chemical method possess several advantages, such as low toxicity, cheap fabrication cost, convenient device processability and adjustable emission wavelengths from ultraviolet to visible and extending to second near infrared window. In addition, they exhibit X-ray excited long persistent luminescence (XEPL) making them suitable for broadening the scope of their applications. This review discusses and summarizes the XEOL and XEPL characteristics of lanthanide doped fluoride NSs. We discuss design strategies and nanostructures that allow manipulation of excitation dynamics in a core–shell geometry to simultaneously produce XEOL, XEPL, as well as photon upconversion and downshifting, enabling emission at multiple wavelengths with a varying time scale profile. The review ends with a discussion of the existing challenges for advancing this field, and presents our subjective insight into areas of further multidisciplinary opportunities.