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

The occurrence of energy transfer (ET) would enhance the luminescence of the activator but sacrifice that of the sensitizer. However, the novel Sm-doped CaTbSnAlO (CTSAO) phosphor reported here seems to be an exception. In the series of CTSAO:Sm phosphors investigated, something unexpected occurs; the activator, Sm, did not gain any energy compensation from the sensitizer, Tb, when temperature increases. Instead, when the loss of Sm luminescence accelerates, simultaneously, the loss of Tb luminescence accordingly alleviates. By careful calculations on the ET efficiency of the CTSAO:0.06Sm phosphor at different temperatures, it is surprisingly found that the efficiency keeps decreasing as temperature increases. It means that the Tb-Sm 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.