Excitation-Power Dependence of Lanthanide-Based Ratiometric Luminescent Nanothermometry

Ratiometric luminescent nanothermometry has emerged as a promising tool for remote thermal mapping at the nanoscale, yet its dependence on excitation power has been largely overlooked. Herein, we investigate the excitation power dependence of lanthanide-based ratiometric luminescent nanothermometers by examining two nonlinear pumping processes of Tm³⁺, where the differing slope factors of two emissions introduce significant intrinsic deviations in the luminescence intensity ratio (LIR) under varying excitation power densities. The robustness of the observed exponential relationship between excitation power density and LIR across different temperatures enables the derivation of a new calibration curve, applicable to any excitation power density. Additionally, analyzing the effect of excitation power on thermometric performance reveals that the absolute thermal sensitivity will change with the excitation power density, while the relative thermal sensitivity remains constant. This study provides valuable insights for optimizing ratiometric luminescent nanothermometry, offering a pathway to more accurate and reliable temperature measurements.