A novel Gd-based phosphor NaGdGeO4:Bi3+,Li+ with super-long ultraviolet-A persistent luminescence

In very recent years, ultraviolet (UV) persistent luminescent materials (PLMs) have attracted widespread attention due to their potential biological applications. However, owing to the lack of suitable emitters and hosts, the design and development of excellent UV PLMs remain challenging. Here, we report a new Gd-based PLM NaGdGeO4:Bi3+ with super-long UVA persistent luminescence (PersL). By further co-doping Li+ ions to increase the concentration of traps, the UVA PersL intensity of NaGdGeO4:Bi3+ is increased by 5.5 times. The optimal NaGdGeO4:Bi3+,Li+ exhibits excellent UVA PersL and can persist for more than 200 h. Moreover, the phosphor NaGdGeO4:Bi3+,Li+ also exhibits photostimulated property with a red LED or NIR laser excitation after the long-term decay, and can be activated by X-ray. This promising Gd-based UVA PLM is expected to have potential applications in biomedicine through triggering photocatalysts or photosensitizers by its UVA PersL to achieve photodynamic therapy and its potential ability of magnetic resonance (MR) imaging due to Gd3+ ions as MR imaging probe contained in the host NaGdGeO4.