UiO‐66(Zr) : Tb3+, Eu3+/PVDF Composite Films as Dual‐Responsive Optical Thermometers for Wide‐Range Temperature Sensing

Abstract Nanothermometers offer unparalleled capabilities for temperature measurement at the nanoscale, with applications in biological systems, microfluidic devices, and catalysis. Among them, fluorescence‐based optical thermometers utilizing Tb 3+ and Eu 3+ ions are promising due to their self‐referenced ratiometric detection and resistance to environmental fluctuations. However, most lanthanide‐based thermometers suffer from reduced sensitivity beyond the cryogenic temperature range, limiting their broader applicability. In this study, we report the synthesis of highly crystalline, Tb 3+ , Eu 3+ codoped UiO‐66(Zr) metal‐organic frameworks via a one‐pot microemulsion approach. These nanothermometers exhibit thermal sensitivity over a wide operational range, from cryogenic to physiological temperatures and beyond. The robust UiO‐66(Zr) framework ensures stability in diverse environments, while the Tb 3+ ‐Eu 3+ energy transfer mechanism provides precise, non‐blinking, ratiometric detection of temperature. Notably, the relative sensitivity of the nanothermometers increases with temperature, achieving superior performance at 400 K, compared to previously reported lanthanide‐terephthalate frameworks. To extend their utility in fluid environments, we fabricated a flexible nanoparticle‐PVDF (polyvinylidene fluoride) composite film that retains the thermal sensitivity of the UMET nanothermometers in isopropyl alcohol. Thus, this study establishes a simple, one‐pot method to incorporate Ln 3+ in the UiO‐66(Zr) framework for optical thermometry above the cryogenic and room temperature ranges, with potential applications in biological and industrial systems.