Dual-ratiometric thermometry of Erbium(Ⅲ) in electrospun fibers inlaid with BaMgF₄ microcrystals

(Ba_1−x−yEr_xYb_y)MgF₄/PAN (BMF-EY/PAN) fibers have been prepared by electrospinning technique, in which composite fibers vested with smooth surface, excellent flexibility and self-calibration temperature sensing function. Under 977 nm laser excitation, the strong green and red up-conversion (UC) emissions produced by the flexible fibers through effective UC luminescence are considered to be a two-photon absorption process, attributing to ²H_11/2/⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 (Ⅰ)/⁴F_9/2 (Ⅱ) → ⁴I_15/2 radiation transitions of Er³⁺, respectively. Combined utilization of green (523 and 545 nm) and red (656 and 669 nm) emissions endows the composite fibers with the potential in microdomain temperature sensing, realizing the accurate temperature acquisition in complex environment. At a relatively moderate working temperature (363 K), the absolute (S_A) and relative (S_R) sensitivity values in fibers based on green-emission reach up to 0.351 and 0.824 %K⁻¹ for main sensing, and correspondingly, the values depended on red-emission are 0.342 and 0.302 %K⁻¹ for auxiliary sensing, respectively. Composite fibers inlaid with crystallites have superior performances in luminescence, thermal feedback and flexibility, providing a breakthrough for the development of temperature-sensing materials in biomedical field.