Energy Gap Linear Superposition of Thermally Coupled Levels toward Enhanced Relative Sensitivity of Ratiometric Thermometry
Yuzhen Wang, Yongsheng Sun, Zhiguo Xia
Abstract
Ratiometric luminescence thermometry (RLT) has attracted considerable attention for its non-invasive, fast response, and strong electromagnetic interference resistance; however, improving relative sensitivity (SR) is of great significance. Herein, we propose a design principle to promote SR by linearly superposing the energy gaps of thermally coupled levels (TCLs) subordinated to luminescence centers. A new fluorescence intensity ratio (FIR′) is derived from multiplying the previous FIRs of multi-pair TCLs. Then, a new SR′ is significantly enhanced and proves to be the sum of the original SR values. The feasibility of this approach is proclaimed by applying to several materials [Na0.5La0.5TiO3:Yb/Nd, Y2O3:Yb/Er, and (LiMg)2Mo3O12:Yb/Er] with improved SR for RLT. Finally, a flexible film is fabricated for temperature measurement of actual scenes and manifests the superiority of the energy gap linear superposition method as ratiometric thermometry.