Speaker
Description
The use of infrared emitting persistent phosphors for medical imaging is an exciting application in the field of persistent luminescence [1]. Current research focuses on host materials doped with Mn2+ or Cr3+, as these transition metals show emission at wavelengths larger than 600 nm, which falls in the tissue transparency window [2]. In this work, we focus on Cr-doped LiGa5O8 (LGO), which is one of the most promising dopant-host combinations for near infrared emission [3].
LGO has an inverse spinel crystal structure, where half of the Ga3+ cations in the host occupy tetrahedral lattice sites and the other cations occupy octahedral sites. Owing to this inverse structure, LGO has a large amount of intrinsic defects, making the host highly suitable as persistent phosphor candidate. Cr dopants substitute for Ga in octahedral sites, leading to NIR emission from the 4T2 and 2E states, after excitation with UV or VIS light. Persistent luminescence is induced by UV excitation and lasts for about 20 min, before the afterglow intensity drops below 0.01 mW cm-2 sr 1. Partial substitution of Ga in the lattice with Ge4+ cations induces additional lattice defects that enhance the persistent luminescence and increases the afterglow time of the Cr3+ emission.
[1] Q. le Masne de Chermont et al., PNAS 104, 9266 (2007).
[2] Y. Zhuang et al., Opt. Mater. 36, 1907 (2014).
[3] F. Liu et al., Sci. Rep. 3, 1554 (2013).
