Red-Emissive Fluorescent Thermometer for Real-Time Monitoring of Intracellular and Architectural Glass Facade Temperature Variations

A red-emissive fluorescent thermometer (bisNAPTPA) with multiple sterically hindered rotary subunits is presented, which enables simultaneous visible measurement of temperature in different conditions. The complex rotary structure of bisNAPTPA produces different output signals in the conditions of organic medium, aqueous solution, and polymeric film that can be applied in monitoring the environmental temperature of cells and glass curtain walls. In both ethyl acetate and aqueous solutions, bisNAPTPA outputs a linear response toward temperatures from 20 to 50 °C with temperature resolutions of 1.464 and 0.598% °C^–1, respectively. Then, the obvious fluorescence switch can be found accompanied with intracellular temperature fluctuation under irradiation of a 980 nm laser. We also fabricated sensor foils by doping different amounts of bisNAPTPA (0.05, 0.1, 0.2, and 0.4 wt %). The obtained foils exhibit good temperature sensitivity (0.514, 0.452, 0.504, and 0.585% °C^–1, respectively) and remarkable linearity in the wide temperature range of 30–90 °C. These foils also exhibit outstanding photostability and thermostability even under a high-power laser (20 mW/cm²) and a temperature of 90 °C. Thus, they are successfully applied to monitor temperature variation in the building equipped with a glass curtain wall unit throughout the day. In summary, we designed an attractive temperature-responsive fluorescent molecule and constructed an environmental temperature monitoring system that can be used for fluorescent sensing in both living cells and modern buildings.