NIR–NIR photon avalanche based luminescent thermometry with Nd³⁺ doped nanoparticles

The recent advances in remote luminescent thermometry give promise for numerous important biomedical applications including temperature T mapping with sub-micrometer spatial resolution and real time kinetics studies within single cells. The ongoing challenge is to find luminophores, which exhibit many exorbitant parameters in a single luminescent nanoparticle, for example, high (e.g. S_R > 2% per K) temperature sensitivities in the physiological temperature range, high luminescence brightness in the NIR spectral region, simplicity and reliability of T readout and mapping. Here, we show an unprecedented approach to luminescent T sensing, which relies on highly temperature dependent non-resonant 1064 nm NIR photoexcitation and a 880 nm anti-Stokes avalanche-like NIR emission from Nd³⁺ doped nanoparticles. The behavior of NaYF₄, Y₂O₃, YGdO₃, YAlO₃, Y₃Al₅O₁₂, LiLaP₄O₁₂, Gd₂O₃ materials and rate-equation modeling suggest that this photon-avalanche phenomenon offers extraordinary features, such as S_R > 4% per K at 300–350 K, high brightness in the NIR region and a double mode, intensity or time-resolved based T readout.