Upconversion thermometer through novel PMMA fiber containing nanocrystals

In this article, nanocrystals were co-doped with polymer for the fabrication of microfibers by using a simple drawing process. The microstructural characteristics of tetragonal-LiYF4:Yb3+/Er3+ nanocrystals were probed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The optical properties such as transmission losses and temperature dependent luminescence of a microfiber were demonstrated under 980 nm excitation. In addition, the fluorescence intensity ratio method (FIR) was utilized to carry out the optical thermometry based on green up-conversion luminescence behavior of nanocrystals in a single microfiber under two thermally coupled levels (2H11/2→4I15/2, 4S3/2→4I15/2) at 522 and 542 nm respectively. The high sensitivity of a microfiber was derived from the FIR technique at 358 K around 0.00307 K−1 in the temperature range of 298-358 K. These results revealed that a single microfiber is promising candidate for applications in optical temperature sensor.