Short-time X-ray irradiation induced long afterglow and photostimulated luminescence from Sr2GeO4: Pr3+

In this paper, Short -time X-ray irradiation induced long afterglow and photostimulated luminescence from Sr2GeO4: Pr3+ has been observed. Under the X-ray irradiation, Sr2GeO4: Pr3+ can produce long afterglow and photostimulated visible luminescence mainly located at 490, 547 and 629 nm, which are attributed to 3P0 -> 3H4, 3P0 -> 3H5 and 3P0 -> 3H6 of Pr3+, respectively. More important, even 5 s X-ray irradiation which was less than the X-ray damage from one CT scan, can induce 5400 s afterglow emission. Furthermore, due to its excellent photostimulated luminescence properties, the afterglow emission intensity of Sr2GeO4: Pr3+can be significantly improved under the radiation of 980 and 808 nm lasers and the emission intensities can still be maintained even after 12 testing cycles. The thermoluminescence results show that Pr3+ doping produces three different traps. Among these, the traps with 0.64 and 0.71 eV trap depth result in excellent X-ray long afterglow luminescence of Sr2GeO4: Pr3+. While the deep trap of 0.96 eV determines the photostimulated luminescence properties. These results indicate that Sr2GeO4:Pr3+ possesses excellent long afterglow and photostimulated luminescence under the X-ray irradiation in safety range, which thus can be regarded as in vivo light source to efficiently conduct photodynamic therapy in the future.