Functional Materials with Wide-Spectral-Responsive Photocatalytic Activity and Real-Time Temperature Feedback: The Electrospun Fibers Embedded with NaGdF₄-Tm-Yb@TiO₂ Nanocrystals

In this work, combining the advantages of upconversion materials, nanofibers, and TiO₂ semiconductors, the composite fibers embedded with NaGdF₄: Tm³⁺, Yb³⁺@TiO₂ nanocrystals (NGF-TY@TiO₂ NCs) are prepared as wide-spectral (UV-NIR) response photocatalysts and temperature sensing materials. Based on the FIR technique, both the thermally (³F_2,3 and ³H₄) and nonthermally (¹G₄ and ³F_2,3) coupled levels of Tm³⁺ are confirmed to be applicable as temperature probes for real-time monitoring and feedback of the working temperature of the catalytic degradation process, and the maximum relative sensitivity values of S_R1 and S_R2 are as high as 2.760%K⁻¹ and 3.019%K⁻¹ at 304 K, respectively. Under 977 nm laser excitation, the energy migration from NGF-T_0.4Y₆ to TiO₂ is demonstrated to a fluorescence resonance energy transfer process. The degradation ratio of rhodamine B (RhB) is 19.3% in the presence of NGF-T_0.4Y₆@TiO₂/PAN fibers and the degradation constant K reaches 0.00117 min⁻¹ after 3 h irradiating from Xe lamp with a UV cutoff filter. Accordingly, this study suggests a new perspective to utilize the NIR energy of sunlight for photocatalytic application based on TiO₂, and the addition of dual temperature feedback provides a reliable reference for the development of safer and more efficient catalytic materials.