In conventional photostimulable storage phosphors, the optical information written by x-ray or ultraviolet irradiation is usually read out as a visible photostimulated luminescence (PSL) signal under the stimulation of a low-energy light with appropriate wavelength. Unlike the transient PSL, here we report a new optical read-out form, photostimulated persistent luminescence (PSPL) in the near-infrared (NIR), from a Cr3+-doped LiGa5O8 NIR persistent phosphor exhibiting a super-long NIR persistent luminescence of more than 1,000 h. An intense PSPL signal peaking at 716 nm can be repeatedly obtained in a period of more than 1,000 h when an ultraviolet-light (250–360 nm) pre-irradiated LiGa5O8:Cr3+ phosphor is repeatedly stimulated with a visible light or a NIR light. The LiGa5O8:Cr3+ phosphor has promising applications in optical information storage, night-vision surveillance, and in vivo bio-imaging.

Near infrared (NIR; 660-1300 nm) long-persistent phosphorescence from Cr(3+) ions with persistence time of more than 1 hour was realized in La(3)Ga(5)GeO(14):Cr(3+) phosphor (with or without co-dopants such as Li(+), Zn(2+), Ca(2+), Mg(2+) and Dy(3+)). The NIR phosphorescence can be effectively achieved under UV illumination (~240-360 nm) but is barely achieved by blue light (~480 nm) irradiation, even though the blue light excitation are effective to the NIR fluorescence. The NIR phosphorescence mechanisms were discussed by measuring the irradiation energy dependence of the phosphorescence intensity.

The luminescence of Pr3+ or Mn2+ singly doped, as well as Pr3+ and Mn2+ codoped, SrB4O7 powder microcrystalline samples were investigated using synchrotron radiation. The photon cascade emission originating from the S01 level was observed in the SrB4O7:Pr3+ (0.1mol%) sample upon 206nm excitation. There are desirable spectral overlaps in the region of 330–430nm between the emission spectra of the SrB4O7:Pr3+ sample and the excitation spectra of the SrB4O7:Mn2+ sample monitoring the Mn2+ luminescence at 640nm. These spectral overlaps are in favor of the energy transfer from Pr3+ to Mn2+, converting the first step photon from Pr3+:S01 in the unpractical ultraviolet or near-ultraviolet regions into the red Mn2+ emission. A comparison of the emission spectra of the SrB4O7:Pr3+, Mn2+ sample with that of the SrB4O7:Pr3+ sample revealed the existence and the efficiency of the proposed energy transfer between Pr3+ and Mn2+, suggesting an promising vacuum ultraviolet phosphor based on Pr3+ and Mn2+ combination with visible quantum efficiency greater than unit.

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