Cr/Er co-doped LaAlO perovskite phosphor: a near-infrared persistent luminescence probe covering the first and third biological windows.

We have developed a novel persistent phosphor of LaAlO perovskite doped with Er, Cr, and Sm (LAO:Er-Cr-Sm), which exhibits long persistent luminescence (PersL) at 1553 nm due to the Er:I→I transition as well as at 734 nm due to the Cr:E(G) →A(F) transition. The intense near-infrared (NIR) PersL bands from Cr and Er match well with the first (NIR-I, 650-950 nm) and third (NIR-III, 1500-1800 nm) biological windows as well as response curves of commercial Si and InGaAs detectors. The photon emission rates of Cr (6.06 × 10 cps sr m) and Er (3.69 × 10 cps sr m) at 60 min after ceasing ultraviolet (UV) illumination were comparable with that of the widely used ZnGaO:Cr red persistent phosphor (5.41 × 10 cps sr m). Furthermore, we also show the first in vitro autofluorescence-free imaging through pork tissues by Si/InGaAs cameras monitoring Cr/Er PersL, and demonstrate that the Er emission can achieve higher spatial resolution than the Cr emission due to the reduced light scattering at longer wavelengths. It is indicated that this material can act as a promising bio-probe for in vivo optical imaging, especially in the NIR-III biological window.