Multiwavelength Fluorescence Intensity Ratio Nanothermometry: High Sensitivity over a Broad Temperature Range

The use of multiple wavelength emissions of rare earth-doped nanomaterials was investigated for optical, nanothermometry, based on a ratiometric technique. A methodology, based on the luminescence associated to different pairs of thermally coupled Stark sublevels, was proposed. This new approach enabled the measurement of broad temperature ranges, in which the absolute sensitivity was optimized. The influence of this multiwavelength fluorescence intensity ratio nanothermometry on the relative temperature sensitivity was also discussed. A proof of concept of the proposed method was done using Er3+-doped Y2O3 nanocrystals as nanoprobes. The obtained results suggested that, with a suitable choice of nanophosphors, optical nanothermometers with high and flat absolute sensitivities in a wide range of temperatures can be tailored using the proposed methodology.