Persistent luminescence ratiometric thermometry

Over the past twenty years, luminescence intensity ratio (LIR)-based temperature sensing technology has become a research hotspot. Despite the great progress in this field, the main limitation of conventional LIR thermometry is the requirement of continuous exposure to excitation source during measurement that may result in thermal effect and thus disturb the accuracy of temperature readout. In order to solve this problem, a new type of thermometry is proposed here, exploiting NaYF4:Er3+ that exhibits long persistent luminescence (PersL) over almost one day. The LIR between the two green PersL bands associated with the 2H11/2→4I15/2 and 4S3/2→4I15/2 electronic transition of Er3+ ions in NaYF4:Er3+ is demonstrated to be a reliable indicator of temperature, which could effectively avoid the long-term exposure to irradiation source. To clearly emphasize the difference between a regular LIR and this research, the newly proposed strategy here is named as persistent luminescence intensity ratio (PLIR) thermometry. The density functional theory and thermoluminescence measurement indicate the PersL mechanism of NaYF4:Er3+ probably stems from the fluorine vacancy related defects. The proposed PLIR thermometry, different from the traditional LIR counterpart, is believed to open a new road to determine temperature via an interesting and reliable way, which will greatly inspire other researchers in the related fields.