Correction Due to Nonthermally Coupled Emission Bands and Its Implications on the Performance of Y₂O₃:Yb³⁺/Er³⁺Single-Particle Thermometers

Lanthanide-doped single dielectric nanoparticles have been exploited toward the realization of temperature sensing in the nanoscale with high spatial, temporal, and thermal resolution. However, due to the relatively small number of emitters when compared with suspensions or powders, the luminescence readouts in individual nanocrystals usually require higher excitation power densities to keep an acceptable signal-to-noise ratio. Since in numerous cases these thermometers work by exploiting upconversion excitation pathways, higher excitation powers can lead to higher-order photon emissions that can overlap with the luminescent bands used to perform the temperature measurements. This work shows that the performance and the characterization of ∼400 nm Y2O3: Yb3+/Er3+ single-particle thermometers vary depending on the excitation irradiance if higher-order spectrally overlapping bands are not properly taken into account. We apply a recently developed method to separate these bands based on their different power-law, without the need for multiple wavelength excitation, resulting in a correction procedure that reduces the temperature readout uncertainty from 0.6 to 0.3 K in the specific case of the thermometer investigated in this work. Additionally, power-excitation-related thermal artifacts on the order of 10 °C were detected and corrected with the presented method.