Unlocking triple-band persistent luminescence: invisible UVC–UVB and visible red emission through structural modulation of Na ₂ SrSi ₂ O ₆ :Pr ³⁺ cyclosilicate

Materials that emit ultraviolet C (UVC) or ultraviolet B (UVB) radiation are essential in domains such as environmental surveillance, public health, and optoelectronic technologies, owing to their elevated photon energy and distinct optical characteristics. However, the development of innovative persistent luminescent phosphors exhibiting emission within the UVC or UVB spectral range continues to pose a considerable challenge. Herein we present a novel Pr³⁺-doped Na₂SrSi₂O₆ phosphor featuring a cyclosilicate framework, which exhibits sustained photon emission in the UVC and UVB regions, alongside luminescence in the red spectral range. The Na₂SrSi₂O₆:Pr³⁺ phosphor demonstrates pronounced and long-lasting UVC, UVB and red persistent luminescence following X-ray excitation, underscoring its effectiveness for utilization in both dark and bright environments. Moreover, the incorporation of smaller ionic radius co-dopants such as Mg²⁺ or Ca²⁺ effectively enhances the red emission intensity of the phosphor. In contrast, the introduction of the larger ionic radius co-dopant Ba²⁺ not only enhances the content of UVC emission but also improves the overall luminescent efficacy. As the content of Ba²⁺ increases, the phosphor exhibits a spectral transition from UVC to UVB within the ultraviolet region. Notably, the applications of this phosphor were assessed in bright-field and dark-field imaging, showcasing its considerable potential for high-contrast monitoring in bright daylight, and advanced optical marking technologies. This work advances the development of visible-to-invisible persistent luminescent materials and offers a good example of engineering the cyclosilicate matrices for luminescence spectrum tuning.