Splendid four-mode optical thermometry design based on thermochromic Cs3GdGe3O9:Er3+ phosphors

Abstract

Optical thermometry has emerged as an inspiring area due to its unique advantages such as contactless operation, rapid response time, excellent spatial resolution, and wide detection range. However, most current luminescent thermometers are based on single-mode detection, and are always subject to the deviation stemming from the insensitivity of temperature in a certain range. Herein, quadruple luminescence thermometric techniques were constructed in thermochromic Cs₃GdGe₃O₉:Er³⁺ phosphors with an almost non-concentration quenching of Er³⁺. Impressively, with elevated temperature, the luminescence color alters evidently from orange to green with a thermo-induced chromaticity shift as high as 0.183, which can be easily discriminated by the naked eye. Benefiting from the different thermo-response of luminescence located at 536, 558 and 660 nm, excellent sensitivities are established on the fluorescence intensity ratio (²H_11/2/⁴S_3/2 and ²H_11/2/⁴F_9/2) and fluorescence decay lifetime (⁴S_3/2) of Er³⁺ single-doped Cs₃GdGe₃O₉ under single-beam light irradiation. The resultant sample shows superior signal discriminability, reversibility and thermal resolution. The outcome of such four-mode thermometry confirms the great potential of Cs₃GdGe₃O₉:Er³⁺ phosphors in optical temperature sensing, including visual sensing of temperature and intelligent high-temperature alarms.