Visible-light and infrared-light persistent phosphors have been extensively studied and are being used as self-sustained glowing tags in darkness. In contrast, persistent phosphors for higher-energy, solar-blind ultraviolet-C wavelengths (200–280 nm) are lacking. Also, persistent tags working in bright environments are unavailable. In this work, we have developed a series of Pr3+-activated silicate-based ultraviolet-C persistent phosphors that can act as self-sustained imaging tags in bright environments. Remarkably, based on the Pr3+-activated ultraviolet-C persistent phosphors, we have also designed and fabricated the first ever Gd3+-activated, Pr3+-sensitized narrowband ultraviolet-B (310313 nm) persistent phosphors through persistent energy transfer from Pr3+ to Gd3+. Moreover, using the same designing strategy, we have developed Gd3+-activated narrowband ultraviolet-B persistent phosphors from Pr3+, Bi3+, or Pb2+-activated ultraviolet-B persistent phosphors.
We firstly identified highly coordinated silicates as the suitable hosts for Pr3+ ultraviolet-C persistent luminescence and synthesized five types of Pr3+-activated silicate-based ultraviolet-C persistent phosphors, including melilite-based aluminosilicates (e.g., Ca2Al2SiO7:Pr3+); alkaline-earth lanthanide cyclosilicates (e.g., Sr3Y2Si6O18:Pr3+); lanthanide oxyorthosilicates (e.g., Lu2SiO5:Pr3+); alkali-earth lanthanide orthosilicates (e.g., LiYSiO4:Pr3+); and silicate garnets (e.g., Ca3Al2Si3O12:Pr3+). These Pr3+-activated ultraviolet-C persistent phosphors can be effectively charged by a standard 254 nm lamp and emit intense, long-lasting (~10 h) afterglow at 265270 nm. Benefitting from the zero solar ultraviolet-C background on the Earth’s surface, the solar-blind ultraviolet-C afterglow can be clearly monitored and imaged by a corona camera in bright environments, enabling the ultraviolet-C persistent phosphors to act as self-sustained, solar-blind glowing tags in bright light.
Based on persistent energy transfer from Pr3+ to Gd3+ 6IJ or 6PJ energy levels, we fabricated the first ever Gd3+-activated narrowband ultraviolet-B persistent phosphors, including Sr3Gd2Si6O18:Pr3+, Ca1.8Gd0.2Al2SiO7:Pr3+, Lu1.8Gd0.2SiO5:Pr3+, Ca2.8Gd0.2Al2Si3O12:Pr3+, LiY0.8Gd0.2SiO4:Pr3+, and Y2GdAl2Ga3O12:Pr3+, by incorporating Gd3+ into the developed Pr3+-activated ultraviolet-C or ultraviolet-B persistent phosphors.
The strategy of designing a Gd3+-activated narrowband ultraviolet-B persistent phosphor from a Pr3+-activated ultraviolet-C or ultraviolet-B persistent phosphor is extended to other persistent sensitizers, i.e., Bi3+ and Pb2+. For examples, we developed the Gd3+-activated, Pb2+-sensitized narrowband ultraviolet-B persistent phosphor, Sr3Gd2Si6O18:Pb2+, based on a new Pb2+-activated ultraviolet-B persistent phosphor, Sr3Y2Si6O18:Pb2+, and the Gd3+-activated, Bi3+-sensitized narrowband ultraviolet-B persistent phosphor Y2GdAl2Ga3O12:Bi3+ based on a new Bi3+-activated ultraviolet-B persistent phosphor Y3Al2Ga3O12:Bi3+.
We firstly identified highly coordinated silicates as the suitable hosts for Pr3+ ultraviolet-C persistent luminescence and synthesized five types of Pr3+-activated silicate-based ultraviolet-C persistent phosphors, including melilite-based aluminosilicates (e.g., Ca2Al2SiO7:Pr3+); alkaline-earth lanthanide cyclosilicates (e.g., Sr3Y2Si6O18:Pr3+); lanthanide oxyorthosilicates (e.g., Lu2SiO5:Pr3+); alkali-earth lanthanide orthosilicates (e.g., LiYSiO4:Pr3+); and silicate garnets (e.g., Ca3Al2Si3O12:Pr3+). These Pr3+-activated ultraviolet-C persistent phosphors can be effectively charged by a standard 254 nm lamp and emit intense, long-lasting (~10 h) afterglow at 265270 nm. Benefitting from the zero solar ultraviolet-C background on the Earth’s surface, the solar-blind ultraviolet-C afterglow can be clearly monitored and imaged by a corona camera in bright environments, enabling the ultraviolet-C persistent phosphors to act as self-sustained, solar-blind glowing tags in bright light.
Based on persistent energy transfer from Pr3+ to Gd3+ 6IJ or 6PJ energy levels, we fabricated the first ever Gd3+-activated narrowband ultraviolet-B persistent phosphors, including Sr3Gd2Si6O18:Pr3+, Ca1.8Gd0.2Al2SiO7:Pr3+, Lu1.8Gd0.2SiO5:Pr3+, Ca2.8Gd0.2Al2Si3O12:Pr3+, LiY0.8Gd0.2SiO4:Pr3+, and Y2GdAl2Ga3O12:Pr3+, by incorporating Gd3+ into the developed Pr3+-activated ultraviolet-C or ultraviolet-B persistent phosphors.
The strategy of designing a Gd3+-activated narrowband ultraviolet-B persistent phosphor from a Pr3+-activated ultraviolet-C or ultraviolet-B persistent phosphor is extended to other persistent sensitizers, i.e., Bi3+ and Pb2+. For examples, we developed the Gd3+-activated, Pb2+-sensitized narrowband ultraviolet-B persistent phosphor, Sr3Gd2Si6O18:Pb2+, based on a new Pb2+-activated ultraviolet-B persistent phosphor, Sr3Y2Si6O18:Pb2+, and the Gd3+-activated, Bi3+-sensitized narrowband ultraviolet-B persistent phosphor Y2GdAl2Ga3O12:Bi3+ based on a new Bi3+-activated ultraviolet-B persistent phosphor Y3Al2Ga3O12:Bi3+.