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.