Ratiometric optical thermometry based on temperature-induced shift of V-O charge transfer band edge

Ratiometric optical thermometry was designed using temperature-induced shift of V-O charge transfer band (CTB) edge combined with temperature-induced variation of Tb³⁺ emission in YV_1-xP_xO₄. P was introduced into YVO₄ lattice to form YV_1-xP_xO₄ solid solution successfully, with the purpose of enhancing Tb³⁺ emission. Under 352 nm excitation which locates in the tail of the V-O CTB, emission spectra of YV_0.3P_0.7O₄:Tb³⁺, Eu³⁺/Sm³⁺ were recorded at a series of temperatures ranging from 300 to 440 K. It is demonstrated that Tb³⁺ and Eu³⁺/Sm³⁺ emissions exhibit opposite temperature dependences. The mechanisms for such opposite variations have been interpreted in detail. Based on the varied fluorescence intensity ratio of Eu³⁺/Sm³⁺ to Tb³⁺ with temperature, high relative sensitivity was obtained with a maximal value of 2.85% K^-1 around 365 K. Our results imply that the proposed strategy is a promising candidate for high-sensitive optical temperature sensing.