Eu³⁺-based luminescence ratiometric thermometry

Recently, luminescence ratiometric thermometry has gained ever-increasing attention due to its merits of rapid response, non-invasiveness, high spatial resolution, and so forth. For research fields relying on temperature measurements, achieving a higher relative sensitivity of this measurement is still an important task. In this work, we developed a strategy for achieving a more sensitive temperature measurement, one merely depending on the photoluminescence of Eu³⁺. We showed that using the ⁵D₁-⁷F₁ transition and the hypersensitive ⁵D₀-⁷F₂ transition of Eu³⁺ can boost the relative sensitivity compared with the method relying on the ⁵D₁-⁷F₁ and ⁵D₀-⁷F₁ transitions of Eu³⁺. The difference between these two strategies was studied and was explained by the hypersensitive ⁵D₀-⁷F₂ transition more steeply decreasing than the ⁵D₀-⁷F₁ transition with a rise in temperature. Our work is expected to help researchers design sensitive optical thermometers via proper use of this hypersensitive transition.