Dual-Feedbacked Temperature Sensing of Er³⁺in Fusiform-Polycrystalline-Implanted BaYF₅/PAN Electrospun Fibers

Ba(Y_1-x-yEr_xYb_y)F₅/polyacrylonitrile (BYF-EY/PAN) composite fibers have been prepared by adopting the electrospinning technology, and fusiform-polycrystalline-implanted fibers can be fused with a thermal response function and excellent flexibility. Upconversion emission displays quadratic and cubical dependence of the photoluminescence intensity on the pumping power, confirming two-photon- and three-photon-induced processes, respectively. Among them, the intense green emission ascribed to²H_11/2/⁴S_3/2→⁴I_15/2transitions is appointed as the main indicator of noncontact temperature sensing, and the faintish blue-violet emission originated from⁴G_11/2/²H_9/2→⁴I_15/2transitions can be served as an auxiliary monitoring channel to calibrate deviation, thereby improving operational accuracy. At a relatively moderate working temperature (363 K), the absolute sensitivity and relative sensitivity of composite fibers reach as high as 0.455 and 0.832% K^-1for main sensing and 0.391 and 2.176% K^-1for auxiliary sensing, respectively. The developed BYF-EY/PAN fiber with outstanding dual-feedbacked temperature sensing is promising to act as flexible sensing elements in fabrics and biomedical devices.