Infrared-photostimulable and long-persistent ultraviolet-emitting phosphor LiLuGeO4:Bi3+,Yb3+ for biophotonic applications

Mater. Chem. Front., 2021,5, 1468-1476 https://pubs.rsc.org/en/content/articlelanding/2021/qm/d0qm00932f/unauth

Photodynamic therapy needing ultraviolet (UV) in deep tissue is hindered due to the low biological tissue penetration ability of UV light. Here, we demonstrate a persistent ultraviolet-emitting phosphor, LiLuGeO4:Bi3+,Yb3+, which can be re-stimulated by near infrared (NIR) light. Yb3+-doping significantly enhances the trap density without changing the thermoluminescence peak positions. The phosphor can be effectively activated by a 254 nm lamp and exhibits prominent persistent luminescence peaking at 350 nm. The decay time can be recorded much longer than 15 h. This phosphor exhibits simulated in vivo photostimulated persistent luminescence after a longtime decay by using in vitro NIR light penetrating biological tissue. Combined with CaAlSiN3:Eu2+, red persistent luminescence from Eu2+ is obtained. LiLuGeO4:Bi3+,Yb3+ makes up the shortage of excellent UVA persistent phosphors. It is expected to have potential applications as an in vivo renewable excitation source to trigger photosensitizers or fluorescent probes when used for biophotonic applications.

Selecting nitride host for Yb3+ toward near-infrared emission with low-energy charge transfer band

Yb3þ-doped phosphors have characteristic near-infrared (NIR) emissions, but their applications in
phosphor-converted light-emitting-diodes (pc-LEDs) and Si solar cells are limited due to their mismatching
excitation spectra. Here, we selected nitride La3Si6N11 (LSN) as host material to achieve Yb3þ
NIR emission upon low-energy charge transfer (CT) excitation. The obtained phosphor LSN:Yb3þ has a
broad CT excitation band ranging from 250 to 500 nm and narrowband NIR emissions ranging from 950
to 1100 nm centered at 983 nm. On the basis of spectral data, the vacuum referred binding energies
(VRBE) schemes are constructed to locate energy levels of all lanthanide ions in LSN. We also fabricated
NIR pc-LED device using 395 nm LED chip to demonstrate the potential applications of LSN:Yb3þ
phosphors.