Excitation-Power Dependence of Lanthanide-Based Ratiometric\nLuminescent Nanothermometry

Ratiometric\nluminescent nanothermometry has emerged as a promising\ntool for remote thermal mapping at the nanoscale, yet its dependence\non excitation power has been largely overlooked. Herein, we investigate\nthe excitation power dependence of lanthanide-based ratiometric luminescent\nnanothermometers by examining two nonlinear pumping processes of Tm<sup>3+</sup>, where the differing slope factors of two emissions introduce\nsignificant intrinsic deviations in the luminescence intensity ratio\n(LIR) under varying excitation power densities. The robustness of\nthe observed exponential relationship between excitation power density\nand LIR across different temperatures enables the derivation of a\nnew calibration curve, applicable to any excitation power density.\nAdditionally, analyzing the effect of excitation power on thermometric\nperformance reveals that the absolute thermal sensitivity will change\nwith the excitation power density, while the relative thermal sensitivity\nremains constant. This study provides valuable insights for optimizing\nratiometric luminescent nanothermometry, offering a pathway to more\naccurate and reliable temperature measurements.