Persistent visible luminescence of SrF2:Pr3+ for ratiometric thermometry.

Luminescence-based thermometry, especially the ratiometric temperature sensing technology, has attracted considerable attention recently due to its characteristics such as non-contact operating mode and strong capacity of resisting disturbance. Differing from the conventional strategy that usually needs continuous excitation, here an optical thermometry, which we have named the persistent luminescence intensity ratio (PLIR) thermometry, is proposed. The PLIR thermometry relies on the optical material SrF2:Pr3+ that could emit luminescence for several hours and even longer after being charged by X-ray. It has been demonstrated that the PLIR is sensitive to the variation of temperature and complies with the Boltzmann distribution. More importantly, the reliability of the proposed PLIR thermometry is verified. Our work may inspire others to develop more persistent luminescence thermometry.

Boltzmann-distribution-dominated persistent luminescence ratiometric thermometry in NaYF4:Pr3.

A novel, to the best of our knowledge, optical temperature measurement method is proposed, i.e., persistent luminescence intensity ratio (PLIR) thermometry. The PLIR thermometry relies on the micro-sized NaYF4:Pr3+ material that can emit persistent luminescence (PersL) uninterruptedly after being charged by x ray irradiation. The 3P1→3H5 and 3P0→3H5 PersL transitions, locating separately at ∼ 522 and 538 nm, have been confirmed to follow the Boltzmann distribution. The emitting intensity ratio of this pair of PersL lines is thus found to be a good indicator of the variation of temperature. Our work is expected to enrich the optical temperature sensing family.