For achieving well-performing optical thermometry, a new type of dual-mode optical thermometer is explored based on the valley-to-peak ratio (VPR) and fluorescence lifetime of Eu3+ emissions in the ZrO2:Eu3+ nanocrystals with sizes down to 10 nm. In the VPR strategy, the intensity ratio between the valley (600 nm) generated by the emission band overlap and the 606 nm peak (5D0→7F2), which is highly temperature sensitive, is employed, giving the maximum relative sensing sensitivity (Sr) of 1.8% K−1 at 293 K and good anti-interference performance. Meanwhile, the 606 nm emission exhibits a temperature-dependent decay lifetime with the highest Sr of 0.33% K−1 at 573 K, which is due to the promoted nonradiative relaxation with temperature. These results provide useful information for constructing high-performance dual-mode optical thermometers, which may further stimulate the development of photosensitive nanomaterials for frontier applications.
