Enlarging Sensitivity of Fluorescence Intensity Ratio-Type Thermometers by the Interruption of the Energy Transfer from a Sensitizer to an Activator

Abstract

The occurrence of energy transfer (ET) would enhance the luminescence of the activator but sacrifice that of the sensitizer. However, the novel Sm³⁺-doped Ca₂TbSn₂Al₃O₁₂ (CTSAO) phosphor reported here seems to be an exception. In the series of CTSAO:xSm³⁺ phosphors investigated, something unexpected occurs; the activator, Sm³⁺, did not gain any energy compensation from the sensitizer, Tb³⁺, when temperature increases. Instead, when the loss of Sm³⁺ luminescence accelerates, simultaneously, the loss of Tb³⁺ luminescence accordingly alleviates. By careful calculations on the ET efficiency of the CTSAO:0.06Sm³⁺ phosphor at different temperatures, it is surprisingly found that the efficiency keeps decreasing as temperature increases. It means that the Tb³⁺-Sm³⁺ energy transfer is capable of being interrupted by an increasing temperature. By simulation, it is found that the occurrence of thermal interruption of energy transfer benefits the achievement of a higher temperature sensing sensitivity. In this sense, making use of the thermal interruption of energy transfer could become a novel route for further design of the fluorescence intensity ratio-type luminescence thermometers.