Dual-mode luminescent core-shell nanoarchitectures for highly sensitive optical nanothermometry

摘要： Currently, FIR-based luminescent nanothermometry has aroused wide concern for its promising applications in fast-moving objects, harsh environments and microscopic temperature. Synchronously promoting the absolute and relative sensitivities of optical thermometers is one of the significant issues at present. In this work, a new nanothermometry strategy to possess both high absolute and relative sensitivities have been proposed by coupling of thermally-coupled-levels-based technique with non-thermally-coupled-levels method in the core-shell designed nanomaterials. Following this strategy, the core-shell-structured NaGdF4:Yb,Er@ NaYF4:Ce,Tb,Eu nanocrystals have been successfully prepared. Remarkably, the adverse cross-relaxation among different activators is extremely suppressed owing to the spatial separation of Er3+ and Eu3+/Tb3+ activators, being conducive to the realization of both intense green upconverting emissions and yellow downshifting luminescence. Moreover, the temperature-sensitive dual-mode luminescent behaviors of core-shell nanomaterials are systematically studied to probe the possible application in FIR-related luminescent thermometry. Specially, the thermally-coupled-levels-based FIR of Er3+ : 2H11/2 / 4I15/2 to Er3+ : 4S3/2 / 4I15/2 and non-thermally-coupled-levels-based FIR of Eu3+ : 5D0 / 7F2 to Tb3+ : 5D4 / 7F6 are proved to be applicable as temperature probes, leading to the achievement of dual-mode temperature sensing. Using the pre-designed core@shell nanoarchitectures, the absolute sensitivity can reach up to 1.02% K-1 based on Eu3+/Tb3+ Stokes emissions and the relative sensitivity could reach as high as 1.12% K-1 based on Er3+ anti-Stokes luminescence. We believe that this study provides a valid approach for developing high-performance optical nanothermometers.