1.5 μm persistent luminescence of Er~(3+) in Gd_3Al_(5-x)Ga_xO_(12) (GAGG) garnets via persistent energy transfer

摘要

Persistent luminescence (PersL) imaging without real-time external excitation has been regarded as the next generationof autofluorescence-free and heating effect-free optical imaging technique. However, in order to acquire improvedspatial resolution and deep penetration depth, developing new near-infrared (NIR) persistent phosphors with intense andlong duration PersL over 1000 nm is still a challenging task. Herein, by utilizing the persistent energy transfer from Ce~(3+)to Er~(3+), we have successfully developed a series of garnet persistent phosphors of Gd_3Al_(5-x)Ga_xO_(12) (x=2.0, 2.5, 3.0, 3.5)doped with Ce~(3+), Cr~(3+) and Er~(3+) ions (GAGG:Ce-Cr-Er), which exhibit long yellow PersL ranging from 480 nm to 780nm mainly due to the 5d-4f parity-allowed transition of Ce~(3+), and NIR PersL in the broad range from 1450 nm to 1670nm due to the typical Er~(3+): ~4I_(13/2)→~4I_(15/2) transition in garnets. Spectroscopic results of photoluminescence (PL), PersL,thermoluminescence (TL) and fluorescence/PersL decay curves of obtained garnet solid-solutions are discussed in detail,which suggest that GAGG:Ce-Cr-Er ganets with multi-wavelength PersL bands can be a potential candidate for longtermin-vivo optical imaging in the third biological window. Moreover, taking advantage of the Gd~(3+) host ion with sevenunpaired electrons in its 4f shell, enhanced positive contrast for magnetic resonance imaging (MRI) also can be expectedusing this material as a T_1-weighted agent. Thus, the GAGG:Ce-Cr-Er persistent phosphor in the form of nano-particlespossesses the possibility as a dual-mode medical diagnosis platform featuring both the deep tissue penetration for in vivobio-imaging and the high spatial resolution for MRI.