X-ray induced long afterglow luminescence from UVC to red region in Ca2P2O7:Pr3+

Abstract

In this paper, we developed low dose X-ray induced long afterglow phosphor Ca2P2O7:Pr3+, which shows excellent afterglow luminescence from ultraviolet C (UVC) to red region. The photoluminescent results show that under 445.7 nm excitation, Ca1.995P2O7:0.5%Pr3+ displays red emissions peaked at 598.3 and 651.9 nm, corresponding to 1D2-3H4 and 3P0-3F2 transitions of Pr3+, respectively. Due to its pure red emission (CIE coordinates (0.59101,0.39926)), Ca1.995P2O7:0.5%Pr3+ can be regarded as a potential LED red phosphor. More importantly, Ca2P2O7:Pr3+ shows long afterglow luminescence from UVC to red region, which consists of four continuous emissions with similar intensity including 260, 359, 466 and 598.3 nm. Since these afterglow continuous emissions are fitted to the absorption of most photodynamic therapy (PDT) agents, Ca2P2O7:Pr3+ can be regarded as excellent PDT agents. Furthermore, 30 s X-ray irradiation can induce 5400 s decay of Ca1.997P2O7:0.3%Pr3+, and its afterglow emission intensity still reaches 5×104 cps after 5400 s decay. Even only 5 s X-ray irradiation also can produce 4.75×104 cps afterglow emission after 10 s decay. In addition, the repeat 980 nm laser irradiations can induce continuous strong photo-stimulated (PSL) luminescent peaks, which can be utilized to conduct high efficiency PDT without another X-ray irradiation. The thermoluminescence results reveal that the existence of shallow (0.89 eV) and deep traps are responsible for the excellent X-ray induced long afterglow and PSL luminescence. All these results suggest that Ca2P2O7:Pr3+ possesses great potential to be regarded as high efficiency PDT agents.