Rational Design of Ratiometric Luminescence Thermometry Based on Thermally Coupled Levels for Bioapplications

Abstract Noninvasive lanthanide‐doped optical thermometers based on fluorescent intensity ratio (FIR) technique have emerged as promising noncontact tools for detecting the inaccessible objects at different scales. Currently, the theoretical and experimental investigations of various influential factors on thermal performances of luminescence thermometers have become one of the hotspots to develop highly sensitive optical thermometers. On the other hand, near‐infrared (NIR) light‐responsive nanothermometers with deep‐tissue penetration have been widely applied for subcutaneous and intracellular thermometry, which could be integrated with optical heating and imaging functions to construct all‐in‐one thermometer‐heater platforms for cancer diagnosis and therapy. In this review, the recent advances in luminescence thermometry based on the thermally coupled levels (TCLs) are elaborately introduced from fundamental aspects to possible biomedical applications, with the perspective and outlook in the emerging challenges of FIR thermometers applied in biomedical science.