Long-persistent luminescence in the near-infrared from Nd3+-doped Sr2SnO4 for in vivo optical imaging

We discovered a new near-infrared (NIR) persistent luminescent material Sr2SnO4:Nd3+, which exhibited NIR luminescence ranging from 850 to 1400 nm. Furthermore, we successfully enhanced the intensity of NIR persistent luminescence by increasing the firing temperature. The intensity of NIR persistent luminescence, which penetrates through a human finger and can be used to visualize a finger vein pattern by using a charge-coupled device camera, reached approximately 1.1 mW/m(2) (lambda = 900 nm) at a decay time of 10 s after ceasing the excitation. We proposed the enhancement process of the NIR persistent luminescence for Sr2SnO4:Nd3+ in conjunction with photoluminescence, absorption, thermoluminescence, and structural properties. (C) 2014 The Japan Society of Applied Physics