Simultaneous luminescence enhancement and lifetime tuning of deep UV-NIR upconversion through controlling dopant concentration

Abstract

Applications of rare-earth (Re)-doped upconversion (UC) micro/nanocrystals in varying areas have sparked a growing, constant demand for deliberate control over the luminescent profile and lifetime. A general strategy for adjusting UC luminescence is to control the dopant Re3+ concentration. However, the progress of elevating dopant concentration is significantly limited owing to frequently encountering severe concentration quenching. Herein, by designing UC system using Tm3+ with super long intermediate energy level lifetime and Yb3+ with a simple two-level structure as a activator/sensitizer combination, we have achieved the unusually intense deep ultraviolet (UV) UC emissions at 290 nm and 345 nm, near UV emission at 361 nm, visible blue emissions at 452 nm and 478 nm, and near infrared (NIR) emission at 803 nm in NaYF4:Yb/Tm microtubes under 980 nm excitation. The luminescence intensity reaches about 56 times and 8 times enhancement for the UV and blue emission, respectively, with the increase of dopant Yb3+ contents from 20 to 80 mol%. While luminescence lifetimes for all emissions decrease, particularly, for NIR emission at 803 nm, from 1507 μs down to 384 μs. Importantly, upon 980 nm irradiation, these UC NaYF4:Yb/Tm microtubes exhibit superior optical performance as a promising candidate of advanced anti-counterfeiting applications and other applications including UV light triggered reactions and multiplexing information storage.